JWT Decoder
Decode JWT header, payload and signature locally.
100% Client-Side · In-Memory Only
Interactive Tool Workspace
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How to Use JWT Decoder
- Paste an encoded JSON Web Token (JWT) string into the token input.
- The tool immediately decodes the Base64Url header and payload sections.
- Inspect claims such as issuer (iss), subject (sub), issued-at (iat), and expiration (exp).
- View human-readable timestamps and a live countdown to token expiry.
Features & Guarantees
- Decodes standard JWTs without sending authorization headers over the internet.
- Real-time expiry validation comparing the exp timestamp against your local machine clock.
- Displays header algorithms and raw cryptographic signature segment.
- Safe for production credentials, OAuth2 bearer tokens, and session cookies.
Frequently Asked Questions
Why should I avoid using public online JWT decoders for production tokens?
Public decoders that transmit tokens to a server can expose sensitive user IDs, roles, and session credentials in server logs or analytics. debug.tools decodes tokens 100% locally.
Does this tool verify the cryptographic signature?
Signature verification requires your secret signing key or public RSA/ECDSA certificate. For security, we never ask for your secrets. We decode the payload and verify expiration locally.