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Security

What is JWT (JSON Web Token)?

A compact, self-contained token format for transmitting claims between parties.

A JSON Web Token (JWT) is a compact, URL-safe token that encodes a JSON payload and signs it cryptographically. JWTs consist of three base64-encoded parts: Header (algorithm), Payload (claims like user ID, roles, expiry), and Signature (verification). The signature uses a secret (HMAC-SHA256) or key pair (RS256). JWTs are stateless — the server doesn't need to look up a session. Common pitfall: JWTs can't be revoked before expiry without a token blocklist.

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