Apostrophe uses Passport to provide single sign-on capabilities. The
apostrophe-passport module is a "universal bridge" compatible with pretty much all Passport strategies that follow best practices, and allows you to implement login via popular services like Google, Twitter, Facebook, Github, and Gitlab, as well as standards like OpenAuth and SAML. To learn more about Passport in general, see the official site for the Passport strategy module.
Apostrophe Passport is not included with the standard Apostrophe distribution and can be installed via npm. For complete details on how to install and configure Apostrophe Passport, see the official documentation on npmjs.org.