JWT Debugger — Decode, Verify & Debug JSON Web Tokens
Paste any JWT to decode its header and payload, check exp/nbf/iat claims against your clock, and verify HS256 signatures with a shared secret — entirely client-side. This free online tool runs entirely in your browser — no data is ever uploaded to a server. How to Use 1. Paste your token — the three base64url parts split and decode automatically. 2. Check the claims table — iss, sub, aud, exp, nbf, iat, jti are broken out with descriptions. 3. Verify the signature — optional secret key; only runs HS256 verification in-browser. 4. Copy any part — header, payload, hex signature, one click each. Example Paste an HS256 token, type the shared secret, and the debugger reports Signature Valid ✓ or Invalid ✗ plus exactly how long the token remains unexpired. Also check out the live tool at freeq.one/tools/jwt-debugger — part of the FreeQ.One suite of free online tools.