Bearer Token Types
There are two types of OAuth2 bearer tokens:
- General Token that represents a string that has no meaning for the client (e.g., 2YotnFZFEjr1zCsicMWpAA). That type of bearer token cannot be validated by the Resource Server without direct communication with an Authorization Server.
- JWT Token represents the JSON object with statements (claims) about the user and token. The JWT token contains three separate parts: header, payload, and signature — each of them are base64-encoded for transferring. JWT tokens are not a part of core OAuth2 specification but mandatory for use with OpenID Connect. JWT token is the most popular way to exchange information about current authentication between microservices. More details can be found here.
Token Validation Methods
OAuth2 tokens can be validated using the following methods: