JSON Web Token (JWT)

A JSON Web Token (JWT) is a compact, signed token that securely carries claims (like a user's identity) between a client and server, commonly used for stateless authentication.

A JWT has three parts — header, payload, and signature — encoded and joined with dots. The payload holds claims such as the user ID and expiry; the signature lets the server verify the token wasn't tampered with.

Because the token is self-contained and signed, the server can authenticate a request without a database lookup, enabling stateless, scalable auth. Tokens should be short-lived and paired with refresh tokens.

JWTs are widely used in API authentication and are issued by identity systems after a user signs in via email or OAuth.

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