JWT Debugger & Inspector
Decode, inspect, and verify JSON Web Token (JWT) headers, payload claims, expiration timestamps, and signature algorithms securely online.
Awaiting Token
Paste a JWT token on the left and click "Decode & Inspect JWT" or click "Load Sample JWT" to examine an example token.
About Tool
Decode, verify, and inspect JSON Web Tokens (JWT) instantly in your browser. Easily inspect token headers, payload claims, expiration timestamps, and verify HMAC-SHA256 signatures with client-side processing for complete privacy and developer security.
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Key Features & Capabilities
- 100% browser-based decoding and signature verification for maximum data privacy
- Real-time breakdown of JWT Header, Payload claims, and raw Signature components
- Instant timestamp conversion for issued at (iat), expiration (exp), and not before (nbf) claims
- Supports signature validation using secret keys or custom algorithms without external API calls
How to Use This Tool
- 1Paste your encoded base64url JWT string (header.payload.signature) into the input box or click 'Load Sample JWT'.
- 2Click 'Decode & Inspect JWT' to view parsed JSON header metadata and user payload claims.
- 3Enter your secret verification key in the signature box and click 'Verify' to validate token authenticity.
Frequently Asked Questions
Is it safe to paste production or private JWT tokens into this debugger?
Yes, completely safe. All token parsing, base64url decoding, and HMAC signature verification execute locally within your browser JavaScript engine. Your secret keys and tokens are never sent to external servers.
Can I verify a JWT signature without knowing the secret key?
No. While you can decode and view the header and payload claims without a secret key, validating the signature's mathematical authenticity requires supplying the secret or public key.
What signing algorithms does this online JWT debugger support?
It supports standard industry algorithms including HMAC SHA-256 (HS256) for secret key verification, as well as RSA and ECDSA public key signature checking.