What is JWT Decoder — Inspect JSON Web Tokens?
The JWT Decoder is an analysis utility that decodes and inspects JSON Web Tokens (JWT) in real time. JWTs are compact, URL-safe containers used for digital identity assertion in web applications. A JWT consists of three parts separated by dots: a Header, a Payload, and a Signature. This tool decodes the Base64Url-encoded header and payload fields, showing you the token claims, issuer, scopes, and expiration details without sending data to a server.
How to Use JWT Decoder — Inspect JSON Web Tokens
- Paste your full encoded JSON Web Token (containing two dots) into the input token field.
- The tool instantly parses the string and splits it into Header, Payload, and Signature blocks.
- Inspect the decoded JSON structures displayed in the colored JSON viewer panels.
- Check the parsed metadata alerts for token state, including the expiration date and issuer details.
Common Use Cases
- Full-stack developers debugging authentication middleware to ensure custom claims are correctly encoded in user tokens.
- Frontend developers inspecting user scopes, roles, and ID token expiration times from OAuth/OIDC flows.
- Security auditors verifying that sensitive or unencrypted data is not accidentally stored in the JWT payload.
Pro Tips & Best Practices
- JWT payloads are encoded, not encrypted. Anyone who intercepts the token can read all client details inside it. Never put sensitive data like passwords or credit cards in a JWT payload.
- Pay attention to the `exp` claim — this is the Unix timestamp indicating when the token ceases to be valid.