JWT Decoder
Decode JSON Web Tokens directly in your browser. No data is sent to any server — your tokens stay on your device.
How to Use the JWT Decoder
1
Paste Your Token
Copy and paste your JWT string into the input field. JWTs have three dot-separated parts: header, payload, signature.
2
Decode Automatically
Click Decode or the tool will auto-decode as you type. The header and payload are Base64URL-decoded and pretty-printed as JSON.
3
Review Expiration & Claims
Check the expiration status, view highlighted claims (sub, iat, exp, iss), and copy the decoded data with one click.
Common JWT Claims Reference
| Claim | Name | Description | Example |
|---|---|---|---|
| sub | Subject | The principal (user ID) that the token represents | 1234567890 |
| iss | Issuer | The issuer of the token | https://auth.example.com |
| aud | Audience | The intended recipient of the token | https://api.example.com |
| exp | Expiration | Unix timestamp when the token expires | 1893456000 |
| nbf | Not Before | Unix timestamp before which the token is not valid | 1516239022 |
| iat | Issued At | Unix timestamp when the token was issued | 1516239022 |
| jti | JWT ID | Unique identifier for the token (prevents replay attacks) | 550e8400-e29b-41d4-a716-446655440000 |
Frequently Asked Questions
Yes. All decoding happens locally in your browser. The JWT is never sent to any server. The signature is not verified (that requires the secret key), but the header and payload are safely decoded client-side.
This tool decodes JWT data but cannot verify the signature without the secret key. Signature verification requires the HMAC secret or RSA public key that only the issuing server knows.
The header contains the algorithm (typ and alg). The payload contains claims like sub (user ID), iat (issued at), exp (expiration), iss (issuer), and custom data. The signature is a cryptographic hash of the header and payload.
The tool automatically checks the "exp" (expiration) claim against the current time and shows whether the token is expired, valid, or will expire soon. It also shows the exact expiration date/time.
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