OpenID Connect Protocol
What is OpenID Connect (OIDC)?
OpenID Connect (OIDC) is an identity layer built on top of the OAuth 2.0 framework. It allows third-party applications to verify the identity of the end-user and to obtain basic user profile information. OIDC uses JSON web tokens (JWTs), which you can obtain using flows conforming to the OAuth 2.0 specifications. See our OIDC Handbook for more details.
OpenID vs. OAuth2
While OAuth 2.0 is about resource access and sharing, OIDC is about user authentication. Its purpose is to give you one login for multiple sites. Each time you need to log in to a website using OIDC, you are redirected to your OpenID site where you log in, and then taken back to the website. For example, if you chose to sign in to Auth0 using your Google account then you used OIDC. Once you successfully authenticate with Google and authorize Auth0 to access your information, Google sends information back to Auth0 about the user and the authentication performed. This information is returned in a JWT. You'll receive an access token and if requested, an ID token.
OpenID and JWTs
JWTs contain claims, which are statements (such as name or email address) about an entity (typically, the user) and additional metadata. The OpenID Connect specification defines a set of standard claims. The set of standard claims include name, email, gender, birth date, and so on. However, if you want to capture information about a user and there currently isn't a standard claim that best reflects this piece of information, you can create custom claims and add them to your tokens.