pleroma/docs/configuration/howto_ejabberd.md

Configuring Ejabberd (XMPP Server) to use Pleroma for authentication

If you want to give your Pleroma users an XMPP (chat) account, you can configure Ejabberd to use your Pleroma server for user authentication, automatically giving every local user an XMPP account.

In general, you just have to follow the configuration described at https://docs.ejabberd.im/admin/configuration/authentication/#external-script. Please read this section carefully.

To get the external script please go to https://github.com/alirizakeles/ejabberd-pleroma-auth and follow the steps described in README.

After restarting your Ejabberd server, your users should now be able to connect with their Pleroma credentials.