synapse/docs/usage/administration/admin_api/README.md

The Admin API

Authenticate as a server admin

Many of the API calls in the admin api will require an access_token for a server admin. (Note that a server admin is distinct from a room admin.)

A user can be marked as a server admin by updating the database directly, e.g.:

UPDATE users SET admin = 1 WHERE name = '@foo:bar.com';

A new server admin user can also be created using the register_new_matrix_user command. This is a script that is located in the scripts/ directory, or possibly already on your $PATH depending on how Synapse was installed.

Finding your user's access_token is client-dependent, but will usually be shown in the client's settings.

Making an Admin API request

Once you have your access_token, you will need to authenticate each request to an Admin API endpoint by providing the token as either a query parameter or a request header. To add it as a request header in cURL:

curl --header "Authorization: Bearer <access_token>" <the_rest_of_your_API_request>

For more details on access tokens in Matrix, please refer to the complete matrix spec documentation.