What is Bearer Token Authentication in Web API?

Bearer Token Authentication in a web API is a security method where the client authenticates itself by including a token, known as a "bearer token," in the HTTP request's Authorization header. This token is typically obtained after the client successfully authenticates with an authorization server, often using OAuth 2.0.

The bearer token represents the user's identity and access permissions. When making API calls, the client sends the token like this:

Authorization: Bearer <token>

The API server then verifies the token to ensure it is valid, unexpired, and authorized to access the requested resource. If the token is valid, the server grants access; otherwise, it returns a 401 Unauthorized error.

Bearer tokens are stateless and convenient for securing APIs. They eliminate the need to store session data on the server while still providing secure access control.