diff --git a/docs/customisations.md b/docs/customisations.md
index 730e9da794..b1ae005276 100644
--- a/docs/customisations.md
+++ b/docs/customisations.md
@@ -1,5 +1,13 @@
 # Customisations
 
+### 🦖 DEPRECATED
+
+Customisations have been deprecated in favour of the [Module API](https://github.com/vector-im/element-web/blob/develop/docs/modules.md).
+If you have use cases from customisations which are not yet available via the Module API please open an issue.
+Customisations will be removed from the codebase in a future release.
+
+---
+
 Element Web and the React SDK support "customisation points" that can be used to
 easily add custom logic specific to a particular deployment of Element Web.
 
diff --git a/webpack.config.js b/webpack.config.js
index 514bf32d06..b77825e396 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -61,6 +61,15 @@ try {
     // stringify the output so it appears in logs correctly, as large files can sometimes get
     // represented as `<Object>` which is less than helpful.
     console.log("Using customisations.json : " + JSON.stringify(fileOverrides, null, 4));
+
+    process.on("exit", () => {
+        console.log(""); // blank line
+        console.warn("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
+        console.warn("!! Customisations have been deprecated and will be removed in a future release      !!");
+        console.warn("!! See https://github.com/vector-im/element-web/blob/develop/docs/customisations.md !!");
+        console.warn("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
+        console.log(""); // blank line
+    });
 } catch (e) {
     // ignore - not important
 }