synapse/docs/admin_api/experimental_features.md

# Experimental Features API

This API allows a server administrator to enable or disable some experimental features on a per-user
basis. The currently supported features are:
- [MSC3881](https://github.com/matrix-org/matrix-spec-proposals/pull/3881): enable remotely toggling push notifications
for another client
- [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575): enable experimental sliding sync support
- [MSC4222](https://github.com/matrix-org/matrix-spec-proposals/pull/4222): adding `state_after` to sync v2

To use it, you will need to authenticate by providing an `access_token`
for a server admin: see [Admin API](../usage/administration/admin_api/).

## Enabling/Disabling Features

This API allows a server administrator to enable experimental features for a given user. The request must
provide a body containing the user id and listing the features to enable/disable in the following format:
```json
{
   "features": {
      "msc3026":true,
      "msc3881":true
   }
}
```
where true is  used to enable the feature, and false is used to disable the feature.


The API is:

```
PUT /_synapse/admin/v1/experimental_features/<user_id>
```

## Listing Enabled Features

To list which features are enabled/disabled for a given user send a request to the following API:

```
GET /_synapse/admin/v1/experimental_features/<user_id>
```

It will return a list of possible features and indicate whether they are enabled or disabled for the
user like so:
```json
{
   "features": {
      "msc3026": true,
      "msc3881": false,
      "msc3967": false
   }
}
```