About this tool
JWT Decoder — Decode JSON Web Tokens to inspect header, payload and signature. Free, fast and private. Runs entirely in your browser at Quick Calci Tools.
Examples
Common scenarios for the JWT Decoder.
Decode a typical access token
- jwt
- eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM…
Header: {alg: HS256, typ: JWT} · Payload: {sub:'123', exp:1735689600}
Spot an expired token
Decoder flags `exp` if it's in the past.
exp = 2024-01-01 → expired 2 years ago.
Who uses the JWT Decoder?
Common scenarios and audiences for this tool.
Backend engineers
Debug OAuth claims during SSO cutovers.
Support staff
Confirm whether a pasted token is structurally valid before escalating.
Pen testers
Review algorithm and claim misuse in capture files.
Tech writers
Illustrate JWT anatomy in security chapters.
Students
Practice reading Base64URL segments without installing jwt-cli.
Frequently asked questions
Everything you need to know about the JWT Decoder.