JWT Decoder & Verifier
A free, private JWT decoder and verifier — header/payload/signature viewer, claims analysis, and HMAC signature verification, entirely in your browser.
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JWT Studio
How to Use the JWT Decoder & Verifier
Paste any JSON Web Token to see its decoded header and payload, analyzed claims with human-readable timestamps and warnings, and optionally verify its HMAC signature against a secret you supply — entirely in your browser via the Web Crypto API.
- 01
Paste a Token
Paste any JWT, or click "Load Example" to see a real, correctly-signed example token.
- 02
Read the Header, Payload & Claims
See the decoded header and payload as formatted JSON, plus a claims table with human-readable expiration/issued-at/not-before analysis and warnings for expired or unusual tokens.
- 03
Verify the Signature (Optional)
Choose the algorithm you expect (HS256/384/512) and enter the secret key to check whether the signature is valid — this never trusts the token’s own declared algorithm.
Frequently Asked Questions
Answers about this tool.
Is my JWT uploaded to a server?
No. Decoding and verification both run entirely inside your browser using the Web Crypto API. Your token is never sent anywhere.
Does decoding a JWT prove it is valid or trustworthy?
No. Decoding only reveals the header and payload — it does not verify the signature. A token can be decoded and read even if it has been tampered with or was never signed at all.
Can this tool verify RS256/ES256 (RSA/ECDSA) tokens?
Not yet — this baseline supports HMAC-signed tokens (HS256/384/512) only. Asymmetric algorithm support is a planned follow-on, since it requires careful PEM/JWK key-format parsing to do correctly.
Related tools
JWT Encoder
Build a new JWT from a header and payload, and sign it with HMAC (HS256/384/512).
Open toolAll JWT Studio tools
Decode a JSON Web Token’s header, payload, and signature, check its claims, verify an HMAC signature, or build and sign a new token. It uses your browser’s Web Crypto API and runs entirely on your device.
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