Single Sign-On (SSO) allows your end users to access your application by verifying their identity with a 3rd party provider instead of providing their credentials directly to your application.
SSO is a good option if your application is associated with a particular platform, if many of your users already use a particular platform, or if you want to reduce signup & login friction by allowing users to click a button instead of entering credentials.
Userfront provides SSO functionality using the Oauth 2.0 standard, which is widely adopted by 3rd party sign-on providers.
See also: SAML
Userfront supports the following list of SSO providers via Oauth 2.0:
Direct support
Support for custom providers