diff --git a/changelog.d/18536.doc b/changelog.d/18536.doc
new file mode 100644
index 0000000000..db57be4a83
--- /dev/null
+++ b/changelog.d/18536.doc
@@ -0,0 +1 @@
+Mark the new module APIs in this release as experimental.
\ No newline at end of file
diff --git a/docs/modules/media_repository_callbacks.md b/docs/modules/media_repository_callbacks.md
index 0cee3384bb..fc37130439 100644
--- a/docs/modules/media_repository_callbacks.md
+++ b/docs/modules/media_repository_callbacks.md
@@ -14,6 +14,11 @@ _First introduced in Synapse v1.132.0_
async def get_media_config_for_user(user_id: str) -> Optional[JsonDict]
```
+**<span style="color:red">
+Caution: This callback is currently experimental . The method signature or behaviour
+may change without notice.
+</span>**
+
Called when processing a request from a client for the
[media config endpoint](https://spec.matrix.org/latest/client-server-api/#get_matrixclientv1mediaconfig).
@@ -39,6 +44,11 @@ _First introduced in Synapse v1.132.0_
async def is_user_allowed_to_upload_media_of_size(user_id: str, size: int) -> bool
```
+**<span style="color:red">
+Caution: This callback is currently experimental . The method signature or behaviour
+may change without notice.
+</span>**
+
Called before media is accepted for upload from a user, in case the module needs to
enforce a different limit for the particular user.
diff --git a/docs/modules/ratelimit_callbacks.md b/docs/modules/ratelimit_callbacks.md
index 3386220e37..30d94024fa 100644
--- a/docs/modules/ratelimit_callbacks.md
+++ b/docs/modules/ratelimit_callbacks.md
@@ -14,6 +14,11 @@ _First introduced in Synapse v1.132.0_
async def get_ratelimit_override_for_user(user: str, limiter_name: str) -> Optional[synapse.module_api.RatelimitOverride]
```
+**<span style="color:red">
+Caution: This callback is currently experimental . The method signature or behaviour
+may change without notice.
+</span>**
+
Called when constructing a ratelimiter of a particular type for a user. The module can
return a `messages_per_second` and `burst_count` to be used, or `None` if
the default settings are adequate. The user is represented by their Matrix user ID
diff --git a/docs/modules/spam_checker_callbacks.md b/docs/modules/spam_checker_callbacks.md
index 6dfa2a7b25..39d7cbc000 100644
--- a/docs/modules/spam_checker_callbacks.md
+++ b/docs/modules/spam_checker_callbacks.md
@@ -254,6 +254,11 @@ _First introduced in Synapse v1.132.0_
async def user_may_send_state_event(user_id: str, room_id: str, event_type: str, state_key: str, content: JsonDict) -> Union["synapse.module_api.NOT_SPAM", "synapse.module_api.errors.Codes"]
```
+**<span style="color:red">
+Caution: This callback is currently experimental . The method signature or behaviour
+may change without notice.
+</span>**
+
Called when processing a request to [send state events](https://spec.matrix.org/latest/client-server-api/#put_matrixclientv3roomsroomidstateeventtypestatekey) to a room.
The arguments passed to this callback are:
|
