JWT Token Validator — Signature Verifier
Decode and validate JWT tokens instantly in your browser. Inspect header and payload claims, check expiry, and verify HMAC signatures (HS256/HS384/HS512). Free and private.
How to Use JWT Token Validator — Signature Verifier
How to Use the JWT Token Validator:
Paste Your Token: Copy your JWT (the three base64url-encoded parts separated by dots) and paste it into the token field. The header and payload decode instantly.
Inspect the Header: The header shows the signing algorithm (alg) and token type (typ). Click to expand or collapse the panel.
Inspect the Payload: The payload contains all claims such as sub, name, iat, exp, and custom claims. The tool highlights registered timing claims (iat, nbf, exp) in a dedicated section.
Check Expiry: The Expiry status card shows whether the token is still active or has expired. The exact exp timestamp is displayed in local time.
Verify the Signature (optional): For HMAC tokens (HS256, HS384, HS512), enter the secret key and click "Verify Signature". The tool uses the Web Crypto API in your browser — your secret never leaves your device.
Copy Claims: Use the Copy button on the Header or Payload panel to copy the decoded JSON for use in your application.
Notes:
- RS256, ES256, and other asymmetric algorithms require the public key; signature verification for these is not supported in the browser.
- Decoding works for any well-formed JWT regardless of algorithm.
- The tool does not validate audience (aud) or issuer (iss) — it only checks structural validity, expiry, and HMAC signature.
Frequently Asked Questions
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