Token
HEADER
PAYLOAD
What is JWT?
JSON Web Token (JWT) is an open standard for securely transmitting information between parties as a JSON object. JWTs are commonly used for authentication and information exchange.
JWT Structure
A JWT consists of three parts separated by dots (header.payload.signature):
1. Header
Contains metadata about the token:
• typ: Token type (usually "JWT")
• alg: Signing algorithm (e.g., "HS256", "RS256")
2. Payload
Contains the actual data and claims:
• Registered claims (optional):
- iss (issuer): Who created the token
- sub (subject): Who the token is about
- exp (expiration time): When the token expires
- iat (issued at): When the token was created
• Public claims: Custom claims defined by the application
• Private claims: Custom claims agreed upon by parties
3. Signature
Verifies the token's authenticity and integrity using the header's algorithm and a secret key.