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Both the id token and the access token usually are only valid for a number of seconds as indicated in the exp claim. In order to prolong the access token, there is the concept of a refresh token that can be user to request a new access token without the users interaction. This allows an application to act on behalf of the user even beyond the users interaction. This is done by issuing a refresh token to the application. The application then can exchange that refresh token for a new access token.

Self-Contained vs Reference Token

A self-contained tokens are tokens that contain the claims inside a protected structure such as an JSON Web Token. The recipient of the token has all the information needed inside the token.

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