diff --git a/app/javascript/mastodon/components/alt_text_badge.tsx b/app/javascript/mastodon/components/alt_text_badge.tsx
new file mode 100644
index 0000000000..99bec1ee51
--- /dev/null
+++ b/app/javascript/mastodon/components/alt_text_badge.tsx
@@ -0,0 +1,67 @@
+import { useState, useCallback, useRef } from 'react';
+
+import { FormattedMessage } from 'react-intl';
+
+import Overlay from 'react-overlays/Overlay';
+import type {
+  OffsetValue,
+  UsePopperOptions,
+} from 'react-overlays/esm/usePopper';
+
+const offset = [0, 4] as OffsetValue;
+const popperConfig = { strategy: 'fixed' } as UsePopperOptions;
+
+export const AltTextBadge: React.FC<{
+  description: string;
+}> = ({ description }) => {
+  const anchorRef = useRef<HTMLButtonElement>(null);
+  const [open, setOpen] = useState(false);
+
+  const handleClick = useCallback(() => {
+    setOpen((v) => !v);
+  }, [setOpen]);
+
+  const handleClose = useCallback(() => {
+    setOpen(false);
+  }, [setOpen]);
+
+  return (
+    <>
+      <button
+        ref={anchorRef}
+        className='media-gallery__alt__label'
+        onClick={handleClick}
+      >
+        ALT
+      </button>
+
+      <Overlay
+        rootClose
+        onHide={handleClose}
+        show={open}
+        target={anchorRef.current}
+        placement='top-end'
+        flip
+        offset={offset}
+        popperConfig={popperConfig}
+      >
+        {({ props }) => (
+          <div {...props} className='hover-card-controller'>
+            <div
+              className='media-gallery__alt__popover dropdown-animation'
+              role='tooltip'
+            >
+              <h4>
+                <FormattedMessage
+                  id='alt_text_badge.title'
+                  defaultMessage='Alt text'
+                />
+              </h4>
+              <p>{description}</p>
+            </div>
+          </div>
+        )}
+      </Overlay>
+    </>
+  );
+};
diff --git a/app/javascript/mastodon/components/media_gallery.jsx b/app/javascript/mastodon/components/media_gallery.jsx
index 35924008b5..84cb4e04dc 100644
--- a/app/javascript/mastodon/components/media_gallery.jsx
+++ b/app/javascript/mastodon/components/media_gallery.jsx
@@ -10,6 +10,7 @@ import ImmutablePropTypes from 'react-immutable-proptypes';
 
 import { debounce } from 'lodash';
 
+import { AltTextBadge } from 'mastodon/components/alt_text_badge';
 import { Blurhash } from 'mastodon/components/blurhash';
 import { formatTime } from 'mastodon/features/video';
 
@@ -97,7 +98,7 @@ class Item extends PureComponent {
     }
 
     if (attachment.get('description')?.length > 0) {
-      badges.push(<span key='alt' className='media-gallery__alt__label'>ALT</span>);
+      badges.push(<AltTextBadge key='alt' description={attachment.get('description')} />);
     }
 
     const description = attachment.getIn(['translation', 'description']) || attachment.get('description');
@@ -156,9 +157,9 @@ class Item extends PureComponent {
       const duration = attachment.getIn(['meta', 'original', 'duration']);
 
       if (attachment.get('type') === 'gifv') {
-        badges.push(<span key='gif' className='media-gallery__gifv__label'>GIF</span>);
+        badges.push(<span key='gif' className='media-gallery__alt__label media-gallery__alt__label--non-interactive'>GIF</span>);
       } else {
-        badges.push(<span key='video' className='media-gallery__gifv__label'>{formatTime(Math.floor(duration))}</span>);
+        badges.push(<span key='video' className='media-gallery__alt__label media-gallery__alt__label--non-interactive'>{formatTime(Math.floor(duration))}</span>);
       }
 
       thumbnail = (
diff --git a/app/javascript/mastodon/features/account_gallery/components/media_item.tsx b/app/javascript/mastodon/features/account_gallery/components/media_item.tsx
index 1a294a74a0..729e40a993 100644
--- a/app/javascript/mastodon/features/account_gallery/components/media_item.tsx
+++ b/app/javascript/mastodon/features/account_gallery/components/media_item.tsx
@@ -5,6 +5,7 @@ import classNames from 'classnames';
 import HeadphonesIcon from '@/material-icons/400-24px/headphones-fill.svg?react';
 import MovieIcon from '@/material-icons/400-24px/movie-fill.svg?react';
 import VisibilityOffIcon from '@/material-icons/400-24px/visibility_off.svg?react';
+import { AltTextBadge } from 'mastodon/components/alt_text_badge';
 import { Blurhash } from 'mastodon/components/blurhash';
 import { Icon } from 'mastodon/components/icon';
 import { formatTime } from 'mastodon/features/video';
@@ -77,11 +78,7 @@ export const MediaItem: React.FC<{
   const badges = [];
 
   if (description && description.length > 0) {
-    badges.push(
-      <span key='alt' className='media-gallery__alt__label'>
-        ALT
-      </span>,
-    );
+    badges.push(<AltTextBadge key='alt' description={description} />);
   }
 
   if (!visible) {
@@ -156,13 +153,19 @@ export const MediaItem: React.FC<{
 
     if (type === 'gifv') {
       badges.push(
-        <span key='gif' className='media-gallery__gifv__label'>
+        <span
+          key='gif'
+          className='media-gallery__alt__label media-gallery__alt__label--non-interactive'
+        >
           GIF
         </span>,
       );
     } else {
       badges.push(
-        <span key='video' className='media-gallery__gifv__label'>
+        <span
+          key='video'
+          className='media-gallery__alt__label media-gallery__alt__label--non-interactive'
+        >
           {formatTime(Math.floor(duration))}
         </span>,
       );
diff --git a/app/javascript/mastodon/locales/en.json b/app/javascript/mastodon/locales/en.json
index b20934388c..e86e300bcb 100644
--- a/app/javascript/mastodon/locales/en.json
+++ b/app/javascript/mastodon/locales/en.json
@@ -85,6 +85,7 @@
   "alert.rate_limited.title": "Rate limited",
   "alert.unexpected.message": "An unexpected error occurred.",
   "alert.unexpected.title": "Oops!",
+  "alt_text_badge.title": "Alt text",
   "announcement.announcement": "Announcement",
   "attachments_list.unprocessed": "(unprocessed)",
   "audio.hide": "Hide audio",
diff --git a/app/javascript/styles/mastodon/components.scss b/app/javascript/styles/mastodon/components.scss
index f3464c83b7..8cb63e42e6 100644
--- a/app/javascript/styles/mastodon/components.scss
+++ b/app/javascript/styles/mastodon/components.scss
@@ -6971,14 +6971,14 @@ a.status-card {
   inset-inline-end: 8px;
   display: flex;
   gap: 2px;
+  pointer-events: none;
 }
 
-.media-gallery__alt__label,
-.media-gallery__gifv__label {
-  display: flex;
-  align-items: center;
-  justify-content: center;
+.media-gallery__alt__label {
+  display: block;
+  text-align: center;
   color: $white;
+  border: 0;
   background: rgba($black, 0.65);
   backdrop-filter: blur(10px) saturate(180%) contrast(75%) brightness(70%);
   padding: 3px 8px;
@@ -6986,8 +6986,41 @@ a.status-card {
   font-size: 12px;
   font-weight: 700;
   z-index: 1;
-  pointer-events: none;
   line-height: 20px;
+  cursor: pointer;
+  pointer-events: auto;
+
+  &--non-interactive {
+    pointer-events: none;
+  }
+}
+
+.media-gallery__alt__popover {
+  background: rgba($black, 0.65);
+  backdrop-filter: blur(10px) saturate(180%) contrast(75%) brightness(70%);
+  border-radius: 4px;
+  box-shadow: var(--dropdown-shadow);
+  padding: 16px;
+  min-width: 16em;
+  min-height: 2em;
+  max-width: 22em;
+  max-height: 30em;
+  overflow-y: auto;
+
+  h4 {
+    font-size: 15px;
+    line-height: 20px;
+    font-weight: 500;
+    color: $white;
+    margin-bottom: 8px;
+  }
+
+  p {
+    font-size: 15px;
+    line-height: 20px;
+    color: rgba($white, 0.85);
+    white-space: pre-line;
+  }
 }
 
 .attachment-list {