Google offers multiple methods of authenticating your app's users in Cloud Platform applications. Each method has different purposes, listed below:
|Firebase Authentication||Provides multiple user authentication options including with Google, Facebook, and Twitter. It also supports the largest number of users while maintaining the smallest amount of code.|
|Google Sign-In||Google Sign-In provides Gmail and G Suite account sign in along with support for one-time passwords (OTP). It's the easiest method of supporting Google-only accounts, or supporting Google accounts in an existing sign-in system.|
|OAuth 2.0 and OpenID Connect||OpenID Connect allows you to handle and use authentication tokens from the ground up with the most customization.|
Firebase Authentication gives you a robust, secure authentication system-in-a-box that helps you do sign in with any account your users want to use. Firebase Authentication supports password authentication in addition to federated sign in with Google, Facebook, Twitter, and more, allowing you to easily scale your authentication system as you grow on desktop and mobile.
Firebase Authentication is the easiest way to set up user authentication for a Google App Engine app. To learn more about Firebase Authentication, try the following:
Firebase Web Tutorial highlights how to use Firebase on a website, including user sign in with Google as the Identity Provider.
If you want to provide a Google login button for your website or app, or you're using G Suite for your domain and you want to authenticate users based on that login, you can use Google Sign-in, which is our sign-in client library built on the OAuth 2.0 and OpenID Connect protocols.
OAuth 2.0 and OpenID Connect
Google Sign-in is based on Google's OAuth 2.0 implementation, which conforms to the OpenID Connect specification, and is OpenID Certified. OAuth 2.0 can be used to implement programmatic authentication to an Identity-Aware Proxy (IAP)-secured resource.
OpenID Connect is an identity layer on top of the OAuth 2.0 protocol, and your app can use it to retrieve user profile information.