What Is a JWT? JSON Web Tokens & Stateless Authentication

What Is a JSON Web Token?

A JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact, self-contained way for securely transmitting information between parties as a JSON object. JWTs are commonly used for stateless user authentication and OAuth 2.0 authorization.

The 3 Parts of a JWT

A JWT string consists of three dot-separated Base64URL-encoded parts:

header.payload.signature
Example: eyJhbGciOiJIUzI1Ni... . eyJzdWIiOiIxMjM0NT... . 4e9g4yWJm7c8VvW2...

Header: Specifies the cryptographic algorithm (e.g. HS256, RS256) and token type (JWT).
Payload: Contains claims (user ID, roles, expiration time).
Signature: Cryptographic hash or signature verifying that the token was not altered in transit.

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