JWT Security Analyzer
Paste a JSON Web Token to decode it and audit its claims for common security problems — alg=none, missing expiry, sensitive data in the payload, and more. Decode only: this tool never verifies the signature. Nothing is uploaded.
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About this tool
Decodes a JWT's header and payload (base64url, no verification) and runs a checklist of the misconfigurations that most often turn tokens into vulnerabilities: alg=none, missing or expired exp, absent iss/aud/nbf, and secret-looking claim names sitting in a payload anyone can read. It deliberately does not verify signatures — that requires your secret or public key, and the checks here are about token structure, not authenticity.
Tokens you paste never leave the page — there is no server, no upload, and no tracking of tool inputs. Still, avoid pasting live production tokens anywhere outside your own systems; use an expired or test token when you can.