diff --git a/latest/CAPTCHA_SETUP.html b/latest/CAPTCHA_SETUP.html
index 1d158654ee..cbc80c2995 100644
--- a/latest/CAPTCHA_SETUP.html
+++ b/latest/CAPTCHA_SETUP.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/CAPTCHA_SETUP.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/account_validity.html b/latest/admin_api/account_validity.html
index 5872506c87..9ec27cf12c 100644
--- a/latest/admin_api/account_validity.html
+++ b/latest/admin_api/account_validity.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/account_validity.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/event_reports.html b/latest/admin_api/event_reports.html
index ca22310610..95c2fac428 100644
--- a/latest/admin_api/event_reports.html
+++ b/latest/admin_api/event_reports.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/event_reports.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/experimental_features.html b/latest/admin_api/experimental_features.html
index 70c8b0f8af..5677617364 100644
--- a/latest/admin_api/experimental_features.html
+++ b/latest/admin_api/experimental_features.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/experimental_features.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/media_admin_api.html b/latest/admin_api/media_admin_api.html
index 075f7cd149..6be0b87dcc 100644
--- a/latest/admin_api/media_admin_api.html
+++ b/latest/admin_api/media_admin_api.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/media_admin_api.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/purge_history_api.html b/latest/admin_api/purge_history_api.html
index 15eff63660..f218f526bc 100644
--- a/latest/admin_api/purge_history_api.html
+++ b/latest/admin_api/purge_history_api.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/purge_history_api.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/register_api.html b/latest/admin_api/register_api.html
index 0383cba0e0..698368bad5 100644
--- a/latest/admin_api/register_api.html
+++ b/latest/admin_api/register_api.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/register_api.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/room_membership.html b/latest/admin_api/room_membership.html
index 39b7fe1c95..899a42f97d 100644
--- a/latest/admin_api/room_membership.html
+++ b/latest/admin_api/room_membership.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/room_membership.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/rooms.html b/latest/admin_api/rooms.html
index 9a83df2352..0b7eea7e9d 100644
--- a/latest/admin_api/rooms.html
+++ b/latest/admin_api/rooms.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/rooms.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/server_notices.html b/latest/admin_api/server_notices.html
index 05749499cc..97c9705f63 100644
--- a/latest/admin_api/server_notices.html
+++ b/latest/admin_api/server_notices.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/server_notices.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/statistics.html b/latest/admin_api/statistics.html
index 68cd0ab232..e87ed37e2b 100644
--- a/latest/admin_api/statistics.html
+++ b/latest/admin_api/statistics.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/statistics.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/user_admin_api.html b/latest/admin_api/user_admin_api.html
index 0dbba7ed61..484a16ab08 100644
--- a/latest/admin_api/user_admin_api.html
+++ b/latest/admin_api/user_admin_api.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/user_admin_api.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/admin_api/version_api.html b/latest/admin_api/version_api.html
index 0f3848599a..b415a0287a 100644
--- a/latest/admin_api/version_api.html
+++ b/latest/admin_api/version_api.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/admin_api/version_api.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/application_services.html b/latest/application_services.html
index 5a8678f8ba..872f40e4ad 100644
--- a/latest/application_services.html
+++ b/latest/application_services.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/application_services.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/auth_chain_difference_algorithm.html b/latest/auth_chain_difference_algorithm.html
index 9979ceb811..882bbba972 100644
--- a/latest/auth_chain_difference_algorithm.html
+++ b/latest/auth_chain_difference_algorithm.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/auth_chain_difference_algorithm.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/code_style.html b/latest/code_style.html
index 3bfc99b110..9e185234ab 100644
--- a/latest/code_style.html
+++ b/latest/code_style.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/code_style.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/consent_tracking.html b/latest/consent_tracking.html
index 2b1a26d7c2..980d2785aa 100644
--- a/latest/consent_tracking.html
+++ b/latest/consent_tracking.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/consent_tracking.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/delegate.html b/latest/delegate.html
index 4c9240d38e..b06972fa66 100644
--- a/latest/delegate.html
+++ b/latest/delegate.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/delegate.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/deprecation_policy.html b/latest/deprecation_policy.html
index 86d86aec0c..d02f0bb871 100644
--- a/latest/deprecation_policy.html
+++ b/latest/deprecation_policy.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/deprecation_policy.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/cas.html b/latest/development/cas.html
index 295ff089d3..9f3e836fbd 100644
--- a/latest/development/cas.html
+++ b/latest/development/cas.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/cas.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/contributing_guide.html b/latest/development/contributing_guide.html
index 5a8b2a54e8..8c388bcbbd 100644
--- a/latest/development/contributing_guide.html
+++ b/latest/development/contributing_guide.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/contributing_guide.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/database_schema.html b/latest/development/database_schema.html
index c4c8020810..8926b4e2cb 100644
--- a/latest/development/database_schema.html
+++ b/latest/development/database_schema.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/database_schema.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/demo.html b/latest/development/demo.html
index f7ef5a3dee..edeffdc5a3 100644
--- a/latest/development/demo.html
+++ b/latest/development/demo.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/demo.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/dependencies.html b/latest/development/dependencies.html
index c0f3b33c7a..15ee44d856 100644
--- a/latest/development/dependencies.html
+++ b/latest/development/dependencies.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/dependencies.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/experimental_features.html b/latest/development/experimental_features.html
index 57d8c6f535..a22d51f4f0 100644
--- a/latest/development/experimental_features.html
+++ b/latest/development/experimental_features.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/experimental_features.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/git.html b/latest/development/git.html
index f4e7fd112a..0d2caf2f5a 100644
--- a/latest/development/git.html
+++ b/latest/development/git.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/git.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/internal_documentation/index.html b/latest/development/internal_documentation/index.html
index 784b13ea00..f52e4d6267 100644
--- a/latest/development/internal_documentation/index.html
+++ b/latest/development/internal_documentation/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/internal_documentation/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/releases.html b/latest/development/releases.html
index f5dbe7549a..0568688f84 100644
--- a/latest/development/releases.html
+++ b/latest/development/releases.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/releases.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/reviews.html b/latest/development/reviews.html
index 29aae57fae..33173b7c85 100644
--- a/latest/development/reviews.html
+++ b/latest/development/reviews.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/reviews.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/room-dag-concepts.html b/latest/development/room-dag-concepts.html
index 48089fdb18..968afe1937 100644
--- a/latest/development/room-dag-concepts.html
+++ b/latest/development/room-dag-concepts.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/room-dag-concepts.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/saml.html b/latest/development/saml.html
index 525265170a..0b04cfff40 100644
--- a/latest/development/saml.html
+++ b/latest/development/saml.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/saml.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/synapse_architecture/cancellation.html b/latest/development/synapse_architecture/cancellation.html
index 646979728e..2a64f227e9 100644
--- a/latest/development/synapse_architecture/cancellation.html
+++ b/latest/development/synapse_architecture/cancellation.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/synapse_architecture/cancellation.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/synapse_architecture/faster_joins.html b/latest/development/synapse_architecture/faster_joins.html
index c204c2a646..02b8c45c84 100644
--- a/latest/development/synapse_architecture/faster_joins.html
+++ b/latest/development/synapse_architecture/faster_joins.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/synapse_architecture/faster_joins.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/development/synapse_architecture/streams.html b/latest/development/synapse_architecture/streams.html
index b7d51c6f29..47b5bf2335 100644
--- a/latest/development/synapse_architecture/streams.html
+++ b/latest/development/synapse_architecture/streams.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/development/synapse_architecture/streams.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/federate.html b/latest/federate.html
index 798e56c31e..df494bd019 100644
--- a/latest/federate.html
+++ b/latest/federate.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/federate.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/index.html b/latest/index.html
index 0a6965d6e2..e87dd10f5b 100644
--- a/latest/index.html
+++ b/latest/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/jwt.html b/latest/jwt.html
index a1e88d8c27..902a2e6b9d 100644
--- a/latest/jwt.html
+++ b/latest/jwt.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/jwt.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/log_contexts.html b/latest/log_contexts.html
index 923a376398..c0c6250df1 100644
--- a/latest/log_contexts.html
+++ b/latest/log_contexts.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/log_contexts.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/manhole.html b/latest/manhole.html
index 5d1d93a7a0..4c8d02f4b6 100644
--- a/latest/manhole.html
+++ b/latest/manhole.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/manhole.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/media_repository.html b/latest/media_repository.html
index 386f5dd412..367943323b 100644
--- a/latest/media_repository.html
+++ b/latest/media_repository.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/media_repository.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/message_retention_policies.html b/latest/message_retention_policies.html
index f51cea6dcf..c7e8218ae4 100644
--- a/latest/message_retention_policies.html
+++ b/latest/message_retention_policies.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/message_retention_policies.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/metrics-howto.html b/latest/metrics-howto.html
index cf735bc7b0..bdb4f9e995 100644
--- a/latest/metrics-howto.html
+++ b/latest/metrics-howto.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/metrics-howto.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/account_data_callbacks.html b/latest/modules/account_data_callbacks.html
index b9968f15bc..78acfa16e6 100644
--- a/latest/modules/account_data_callbacks.html
+++ b/latest/modules/account_data_callbacks.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/account_data_callbacks.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/account_validity_callbacks.html b/latest/modules/account_validity_callbacks.html
index af8c027580..ec12116d63 100644
--- a/latest/modules/account_validity_callbacks.html
+++ b/latest/modules/account_validity_callbacks.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/account_validity_callbacks.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/add_extra_fields_to_client_events_unsigned.html b/latest/modules/add_extra_fields_to_client_events_unsigned.html
index f004a2601a..95989ce728 100644
--- a/latest/modules/add_extra_fields_to_client_events_unsigned.html
+++ b/latest/modules/add_extra_fields_to_client_events_unsigned.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/add_extra_fields_to_client_events_unsigned.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/background_update_controller_callbacks.html b/latest/modules/background_update_controller_callbacks.html
index 83b5cd2e4e..e594719d8f 100644
--- a/latest/modules/background_update_controller_callbacks.html
+++ b/latest/modules/background_update_controller_callbacks.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/background_update_controller_callbacks.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/index.html b/latest/modules/index.html
index 629c6997c6..e39f866bed 100644
--- a/latest/modules/index.html
+++ b/latest/modules/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/password_auth_provider_callbacks.html b/latest/modules/password_auth_provider_callbacks.html
index 7b07acdfe1..cd8f716858 100644
--- a/latest/modules/password_auth_provider_callbacks.html
+++ b/latest/modules/password_auth_provider_callbacks.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/password_auth_provider_callbacks.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/porting_legacy_module.html b/latest/modules/porting_legacy_module.html
index 7d4b928be4..c6856f74f1 100644
--- a/latest/modules/porting_legacy_module.html
+++ b/latest/modules/porting_legacy_module.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/porting_legacy_module.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/presence_router_callbacks.html b/latest/modules/presence_router_callbacks.html
index 1b0457de7c..4853c1ccdb 100644
--- a/latest/modules/presence_router_callbacks.html
+++ b/latest/modules/presence_router_callbacks.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/presence_router_callbacks.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/spam_checker_callbacks.html b/latest/modules/spam_checker_callbacks.html
index 2092387123..1f7b8c444a 100644
--- a/latest/modules/spam_checker_callbacks.html
+++ b/latest/modules/spam_checker_callbacks.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/spam_checker_callbacks.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/third_party_rules_callbacks.html b/latest/modules/third_party_rules_callbacks.html
index c601154292..5c28e04068 100644
--- a/latest/modules/third_party_rules_callbacks.html
+++ b/latest/modules/third_party_rules_callbacks.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/third_party_rules_callbacks.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/modules/writing_a_module.html b/latest/modules/writing_a_module.html
index ac3ac5555f..0d322fb7ba 100644
--- a/latest/modules/writing_a_module.html
+++ b/latest/modules/writing_a_module.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/modules/writing_a_module.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/openid.html b/latest/openid.html
index aa3e89e411..d6a035bba9 100644
--- a/latest/openid.html
+++ b/latest/openid.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/openid.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/opentracing.html b/latest/opentracing.html
index ba7d761511..256b5e431f 100644
--- a/latest/opentracing.html
+++ b/latest/opentracing.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/opentracing.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/other/running_synapse_on_single_board_computers.html b/latest/other/running_synapse_on_single_board_computers.html
index 8748aa7ca3..b12d523201 100644
--- a/latest/other/running_synapse_on_single_board_computers.html
+++ b/latest/other/running_synapse_on_single_board_computers.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/other/running_synapse_on_single_board_computers.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/password_auth_providers.html b/latest/password_auth_providers.html
index dd897217b9..ceb5e239f0 100644
--- a/latest/password_auth_providers.html
+++ b/latest/password_auth_providers.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/password_auth_providers.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/postgres.html b/latest/postgres.html
index 5d5a8fa048..d39f036fe8 100644
--- a/latest/postgres.html
+++ b/latest/postgres.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/postgres.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/print.html b/latest/print.html
index 862fae48da..15bb27e0fa 100644
--- a/latest/print.html
+++ b/latest/print.html
@@ -150,7 +150,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/print.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/replication.html b/latest/replication.html
index c6603a8303..a56264312b 100644
--- a/latest/replication.html
+++ b/latest/replication.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/replication.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/reverse_proxy.html b/latest/reverse_proxy.html
index 2886a8e7a0..694cddb4f7 100644
--- a/latest/reverse_proxy.html
+++ b/latest/reverse_proxy.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/reverse_proxy.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/room_and_user_statistics.html b/latest/room_and_user_statistics.html
index 3edb01aa67..81e231f8c3 100644
--- a/latest/room_and_user_statistics.html
+++ b/latest/room_and_user_statistics.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/room_and_user_statistics.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/server_notices.html b/latest/server_notices.html
index a0a2fd3f48..511a312656 100644
--- a/latest/server_notices.html
+++ b/latest/server_notices.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/server_notices.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/setup/forward_proxy.html b/latest/setup/forward_proxy.html
index cfbcecc4b0..e8d99e94f0 100644
--- a/latest/setup/forward_proxy.html
+++ b/latest/setup/forward_proxy.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/setup/forward_proxy.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/setup/installation.html b/latest/setup/installation.html
index 3522e4d4b6..412c1b05e9 100644
--- a/latest/setup/installation.html
+++ b/latest/setup/installation.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/setup/installation.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/setup/turn/coturn.html b/latest/setup/turn/coturn.html
index 72c55baae7..6892471a1e 100644
--- a/latest/setup/turn/coturn.html
+++ b/latest/setup/turn/coturn.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/setup/turn/coturn.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/setup/turn/eturnal.html b/latest/setup/turn/eturnal.html
index 9b098a0257..c1a5e4ba83 100644
--- a/latest/setup/turn/eturnal.html
+++ b/latest/setup/turn/eturnal.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/setup/turn/eturnal.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/sso_mapping_providers.html b/latest/sso_mapping_providers.html
index cb926ac91b..ed1a67f191 100644
--- a/latest/sso_mapping_providers.html
+++ b/latest/sso_mapping_providers.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/sso_mapping_providers.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/structured_logging.html b/latest/structured_logging.html
index 5b7418afb9..5f34e952ca 100644
--- a/latest/structured_logging.html
+++ b/latest/structured_logging.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/structured_logging.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/synctl_workers.html b/latest/synctl_workers.html
index 727373309a..ff11f47d60 100644
--- a/latest/synctl_workers.html
+++ b/latest/synctl_workers.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/synctl_workers.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/systemd-with-workers/index.html b/latest/systemd-with-workers/index.html
index 7f95aec9a1..536afb213a 100644
--- a/latest/systemd-with-workers/index.html
+++ b/latest/systemd-with-workers/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/systemd-with-workers/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/tcp_replication.html b/latest/tcp_replication.html
index 8b26ce4cd4..252bb78801 100644
--- a/latest/tcp_replication.html
+++ b/latest/tcp_replication.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/tcp_replication.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/templates.html b/latest/templates.html
index 4266bdc452..fe10ae2283 100644
--- a/latest/templates.html
+++ b/latest/templates.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/templates.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/turn-howto.html b/latest/turn-howto.html
index e818561b70..b5e85d0ea2 100644
--- a/latest/turn-howto.html
+++ b/latest/turn-howto.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/turn-howto.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/upgrade.html b/latest/upgrade.html
index 7e28d01e1d..78fc37c9f3 100644
--- a/latest/upgrade.html
+++ b/latest/upgrade.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/upgrade.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/admin_api/background_updates.html b/latest/usage/administration/admin_api/background_updates.html
index 499f27c4db..cbadb4fa40 100644
--- a/latest/usage/administration/admin_api/background_updates.html
+++ b/latest/usage/administration/admin_api/background_updates.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/admin_api/background_updates.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/admin_api/federation.html b/latest/usage/administration/admin_api/federation.html
index 7fc104437c..0da3c60cdb 100644
--- a/latest/usage/administration/admin_api/federation.html
+++ b/latest/usage/administration/admin_api/federation.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/admin_api/federation.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/admin_api/index.html b/latest/usage/administration/admin_api/index.html
index f09b4462a4..50504f9e30 100644
--- a/latest/usage/administration/admin_api/index.html
+++ b/latest/usage/administration/admin_api/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/admin_api/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/admin_api/registration_tokens.html b/latest/usage/administration/admin_api/registration_tokens.html
index d01834b7bb..731b2e7402 100644
--- a/latest/usage/administration/admin_api/registration_tokens.html
+++ b/latest/usage/administration/admin_api/registration_tokens.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/admin_api/registration_tokens.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/admin_faq.html b/latest/usage/administration/admin_faq.html
index d771ea5dc1..34b931c73e 100644
--- a/latest/usage/administration/admin_faq.html
+++ b/latest/usage/administration/admin_faq.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/admin_faq.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/database_maintenance_tools.html b/latest/usage/administration/database_maintenance_tools.html
index 69a78a90d6..55135a920e 100644
--- a/latest/usage/administration/database_maintenance_tools.html
+++ b/latest/usage/administration/database_maintenance_tools.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/database_maintenance_tools.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/index.html b/latest/usage/administration/index.html
index 515c40611e..bc42588a4a 100644
--- a/latest/usage/administration/index.html
+++ b/latest/usage/administration/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/monitoring/reporting_homeserver_usage_statistics.html b/latest/usage/administration/monitoring/reporting_homeserver_usage_statistics.html
index 901a6c0de0..b39f61d10d 100644
--- a/latest/usage/administration/monitoring/reporting_homeserver_usage_statistics.html
+++ b/latest/usage/administration/monitoring/reporting_homeserver_usage_statistics.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/monitoring/reporting_homeserver_usage_statistics.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/monthly_active_users.html b/latest/usage/administration/monthly_active_users.html
index 6efacdf47a..b7b9172866 100644
--- a/latest/usage/administration/monthly_active_users.html
+++ b/latest/usage/administration/monthly_active_users.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/monthly_active_users.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/request_log.html b/latest/usage/administration/request_log.html
index adf42d8f6d..b01405aee5 100644
--- a/latest/usage/administration/request_log.html
+++ b/latest/usage/administration/request_log.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/request_log.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/state_groups.html b/latest/usage/administration/state_groups.html
index 3136f29dd1..4442ff7fb9 100644
--- a/latest/usage/administration/state_groups.html
+++ b/latest/usage/administration/state_groups.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/state_groups.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/understanding_synapse_through_grafana_graphs.html b/latest/usage/administration/understanding_synapse_through_grafana_graphs.html
index 9fa2b487ec..fe1732c4c7 100644
--- a/latest/usage/administration/understanding_synapse_through_grafana_graphs.html
+++ b/latest/usage/administration/understanding_synapse_through_grafana_graphs.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/understanding_synapse_through_grafana_graphs.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/administration/useful_sql_for_admins.html b/latest/usage/administration/useful_sql_for_admins.html
index 37f3b8c213..c79c87202e 100644
--- a/latest/usage/administration/useful_sql_for_admins.html
+++ b/latest/usage/administration/useful_sql_for_admins.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/administration/useful_sql_for_admins.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/config_documentation.html b/latest/usage/configuration/config_documentation.html
index c0b3f44ce9..23b14a35e7 100644
--- a/latest/usage/configuration/config_documentation.html
+++ b/latest/usage/configuration/config_documentation.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/config_documentation.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/homeserver_sample_config.html b/latest/usage/configuration/homeserver_sample_config.html
index 965a308d9f..1472bfc74a 100644
--- a/latest/usage/configuration/homeserver_sample_config.html
+++ b/latest/usage/configuration/homeserver_sample_config.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/homeserver_sample_config.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/index.html b/latest/usage/configuration/index.html
index 81f3e1647a..f00a6530b1 100644
--- a/latest/usage/configuration/index.html
+++ b/latest/usage/configuration/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/logging_sample_config.html b/latest/usage/configuration/logging_sample_config.html
index a12ad8b96d..0700a88f46 100644
--- a/latest/usage/configuration/logging_sample_config.html
+++ b/latest/usage/configuration/logging_sample_config.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/logging_sample_config.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/user_authentication/index.html b/latest/usage/configuration/user_authentication/index.html
index 4fd169364b..004cdc9928 100644
--- a/latest/usage/configuration/user_authentication/index.html
+++ b/latest/usage/configuration/user_authentication/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/user_authentication/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/user_authentication/refresh_tokens.html b/latest/usage/configuration/user_authentication/refresh_tokens.html
index 2caa7c9c0f..dd33666cff 100644
--- a/latest/usage/configuration/user_authentication/refresh_tokens.html
+++ b/latest/usage/configuration/user_authentication/refresh_tokens.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/user_authentication/refresh_tokens.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/user_authentication/single_sign_on/cas.html b/latest/usage/configuration/user_authentication/single_sign_on/cas.html
index 8f8cda4024..2feb9533f7 100644
--- a/latest/usage/configuration/user_authentication/single_sign_on/cas.html
+++ b/latest/usage/configuration/user_authentication/single_sign_on/cas.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/user_authentication/single_sign_on/cas.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/user_authentication/single_sign_on/index.html b/latest/usage/configuration/user_authentication/single_sign_on/index.html
index 0ccfd922bc..d8b49f1e73 100644
--- a/latest/usage/configuration/user_authentication/single_sign_on/index.html
+++ b/latest/usage/configuration/user_authentication/single_sign_on/index.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/user_authentication/single_sign_on/index.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/usage/configuration/user_authentication/single_sign_on/saml.html b/latest/usage/configuration/user_authentication/single_sign_on/saml.html
index 62be5445f0..adeb387929 100644
--- a/latest/usage/configuration/user_authentication/single_sign_on/saml.html
+++ b/latest/usage/configuration/user_authentication/single_sign_on/saml.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/usage/configuration/user_authentication/single_sign_on/saml.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/user_directory.html b/latest/user_directory.html
index b95569ae44..524c1d4d96 100644
--- a/latest/user_directory.html
+++ b/latest/user_directory.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/user_directory.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/welcome_and_overview.html b/latest/welcome_and_overview.html
index 0a6965d6e2..6da90f4649 100644
--- a/latest/welcome_and_overview.html
+++ b/latest/welcome_and_overview.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/welcome_and_overview.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">
diff --git a/latest/workers.html b/latest/workers.html
index 9834649988..cf1d5e92b4 100644
--- a/latest/workers.html
+++ b/latest/workers.html
@@ -152,7 +152,24 @@
                     });
                 </script>
 
-                <div id="content" class="content">
+                <!--BEGIN OUTDATED WARNING-->
+<div style="padding: 2em; margin: 2em; border: 3px solid red;" class="content">
+    <h1>This documentation may be out of date!</h1>
+
+    <p>
+        This documentation site is for the versions of Synapse maintained by the <em>Matrix.org Foundation</em> (<a href="https://github.com/matrix-org/synapse">github.com/matrix-org/synapse</a>), available under the Apache 2.0 licence.
+    </p>
+
+    <p>
+        Since version 1.99, Synapse is now maintained by <em>Element</em> under a new licence (<a href="https://github.com/element-hq/synapse">github.com/element-hq/synapse</a>).
+    </p>
+
+    <p>
+        If you are interested in the documentation for a later version of Synapse, please <a href="https://element-hq.github.io/synapse/latest/workers.html">click here to navigate to this same page on the latest Element Synapse documentation site</a>, if it's available.
+    </p>
+</div>
+<!--END OUTDATED WARNING-->
+<div id="content" class="content">
                     <main>
                         <!-- Page table of contents -->
                         <div class="sidetoc">