Cybersecurity

What is JSON Web Token?

Quick answer

A compact, signed token format used to securely pass identity and permission claims between a client and a server.

JSON Web Token, explained

A JSON Web Token (JWT, often pronounced jot) has three parts separated by dots: a header describing the signing algorithm, a payload containing claims such as a user ID and expiry time, and a signature. The header and payload are encoded, not encrypted, so anyone can read them, but the signature lets a server verify that the token has not been altered.

JWTs are common in modern authentication. After a user logs in, the server issues a token, and the client sends it with each request, so the server does not need to look up a session every time. Best practices include short expiry times, secure storage, never putting secrets in the payload, and validating signatures and algorithms strictly.

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