diff --git a/changelogs/client_server/newsfragments/3100.feature b/changelogs/client_server/newsfragments/3100.feature
new file mode 100644
index 00000000..259f1958
--- /dev/null
+++ b/changelogs/client_server/newsfragments/3100.feature
@@ -0,0 +1 @@
+Add `<details>` and `<summary>` to the suggested HTML subset as per [MSC2184](https://github.com/matrix-org/matrix-doc/pull/2184).
\ No newline at end of file
diff --git a/content/client-server-api/modules/instant_messaging.md b/content/client-server-api/modules/instant_messaging.md
index 8e6df01d..3a933a93 100644
--- a/content/client-server-api/modules/instant_messaging.md
+++ b/content/client-server-api/modules/instant_messaging.md
@@ -53,7 +53,7 @@ tags to permit, denying the use and rendering of anything else, is:
 `font`, `del`, `h1`, `h2`, `h3`, `h4`, `h5`, `h6`, `blockquote`, `p`,
 `a`, `ul`, `ol`, `sup`, `sub`, `li`, `b`, `i`, `u`, `strong`, `em`,
 `strike`, `code`, `hr`, `br`, `div`, `table`, `thead`, `tbody`, `tr`,
-`th`, `td`, `caption`, `pre`, `span`, `img`.
+`th`, `td`, `caption`, `pre`, `span`, `img`, `details`, `summary`.
 
 Not all attributes on those tags should be permitted as they may be
 avenues for other disruption attempts, such as adding `onclick` handlers