JWT Decoder
Decode any JSON Web Token instantly. View header, payload and signature. Check expiry and claims. Runs entirely in your browser.
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What is JWT?
JSON Web Tokens are a compact way to securely transmit information between parties. They are widely used for authentication and authorization.
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What this decodes
The header (algorithm and token type), payload (claims like user ID, roles, expiry) and the signature block (cannot be verified without the secret).
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100% private
Your JWT never leaves your browser. Decoding happens entirely client-side — never share real tokens with online tools that send them to servers.
Frequently Asked Questions
What is a JWT?
A JSON Web Token (JWT) is a compact, URL-safe token format used for authentication. It consists of three Base64url-encoded parts separated by dots: a header (algorithm info), a payload (claims/data), and a signature for verification.
Can you verify the JWT signature?
Signature verification requires the secret key or public key used to sign the token. Since this tool runs in your browser and has no server, it cannot verify signatures. It decodes and displays the header and payload claims only.
Is it safe to paste my JWT here?
This tool runs entirely in your browser — your JWT is never transmitted to any server. However, be cautious about pasting real production tokens into any online tool. Use test tokens where possible.