It's a web UI tool you can use to **administrate users and rooms on your Matrix server**. It's designed to work with the Synapse homeserver implementation, but to some extent may work with [Dendrite](./configuring-playbook-dendrite.md) as well.
**Note**: Synapse Admin requires Synapse's [Admin APIs](https://matrix-org.github.io/synapse/latest/usage/administration/admin_api/index.html) to function. Access to them is restricted with a valid access token, so exposing them publicly should not be a real security concern. Still, for additional security, we normally leave them unexposed, following [official Synapse reverse-proxying recommendations](https://github.com/element-hq/synapse/blob/master/docs/reverse_proxy.md#synapse-administration-endpoints). Because Synapse Admin needs these APIs to function, when installing Synapse Admin, the playbook **automatically** exposes the Synapse Admin API publicly for you. Depending on the homeserver implementation you're using (Synapse, Dendrite), this is equivalent to:
By default, synapse-admin installation will be [restricted to only work with one homeserver](https://github.com/Awesome-Technologies/synapse-admin/blob/e21e44362c879ac41f47c580b04210842b6ff3d7/README.md#restricting-available-homeserver) - the one managed by the playbook. To adjust these restrictions, tweak the `matrix_synapse_admin_config_restrictBaseUrl` variable.
