JWT Debugger & Signature Verifier
Inspect, decode, and check JSON Web Tokens (JWT) locally. Edit header or payload data, update signing secrets, and verify signatures dynamically without sending data to the server.
Encoded Raw JWT Token
Signature Unsigned / Secret Empty
Please enter a valid cryptographic secret on the payload panel to sign.
HEADER: ALGORITHM & TOKEN TYPE
PAYLOAD: DATA / CLAIM DATA
VERIFY SIGNATURE / HS256 SECRET
What this tool does
Inspect, format, or process datasets securely inside your local browser cache.
How to use it
- 1Enter or upload your source data files.
- 2Select parsing parameters or target configuration rules.
- 3Copy resulting strings or download output files.
What would you like to do next?
Explore other free local tools
Did you know?
We process your documents privately in local sandbox storage. Your actual data remains in your browser tab. We never log, view, or store file contents.
About jwt debugger free
Decode payload headers and sign HS256 JWT tokens 100% locally in your web browser. Decode a JSON Web Token to inspect its header and claims, see exactly when it was issued and when it expires, and verify an HS256 signature against your secret. Tokens carry user IDs and session data, so this runs entirely in your browser rather than sending a live token to someone else's server.
How to Use This Tool in 3 Easy Steps
Paste the token
Drop in the full header.payload.signature string, for example from an Authorization header.
Read the claims
Header and payload are decoded, with exp and iat converted to readable dates.
Verify the signature
Enter the HS256 secret to confirm the token was signed with it and has not been altered.
Why Users Choose SolveMyPDF
- ✓Header and payload decoded: See the algorithm, token type and every claim without writing a line of code.
- ✓Readable timestamps: exp and iat shown as dates, so an expired token is obvious immediately.
- ✓HS256 verification and signing: Check a signature against your secret, or sign a test token for local development.
- ✓Runs locally: Verification uses the browser's built-in Web Crypto API. The token and secret stay on your machine.
Frequently Asked Questions
Is decoding a token the same as verifying it?
No. A JWT's header and payload are only Base64URL-encoded, so anyone can decode them. Verification is what proves the token was signed with your secret and has not been tampered with — never trust decoded claims that have not been verified.
Can it verify RS256 or ES256 tokens?
Not currently. Signature verification supports HS256 (HMAC with SHA-256), which uses a shared secret. Tokens signed with RS256 or ES256 can still be decoded here, but verifying them needs the issuer's public key.
Is it safe to paste a production token?
The token is decoded in your browser and not transmitted. Even so, treat a live token like a password: it grants access until it expires, so avoid pasting one anywhere you would not paste a password.