> ## Documentation Index
> Fetch the complete documentation index at: https://devdocs.xbox.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication and S2S

> How titles authenticate with XBOX Live and make service-to-service REST calls, covering custom service config, XSTS tokens, and S2S auth flow.

This section describes how to authenticate with XBOX services, and make service-to-service calls to XBOX services from the title.

## In this section

[Custom service configuration](/services/xbox-services/fundamentals/s2s-auth-calls/custom-service-config/live-custom-services-config-nav)
Overview of custom game service configuration in Partner Center.

[Service calls to XBOX services](/services/xbox-services/fundamentals/s2s-auth-calls/s2s-calls/live-s2s-calls-nav)
Authenticating through XBOX services.

[XBOX services authentication](/services/xbox-services/fundamentals/s2s-auth-calls/service-authentication/live-service-authentication-nav)
Provides information about XBOX services authentication and tokens.


## Related topics

- [Service-to-service multiplayer session management](/services/xbox-services/fundamentals/s2s-auth-calls/s2s-calls/s2s-call-patterns/live-mpsd-service-to-service.md)
- [Optional services](/build/gdk-and-engines/optional-services.md)
- [S2s calls](/services/xbox-services/fundamentals/s2s-auth-calls/s2s-calls/index.md)
- [S2s auth calls](/services/xbox-services/fundamentals/s2s-auth-calls/index.md)
- [S2s call patterns](/services/xbox-services/fundamentals/s2s-auth-calls/s2s-calls/s2s-call-patterns/index.md)