JWT Decoder
Decode JWT tokens instantly. Header, payload, claims — all client-side.
About the JWT Decoder
This JWT decoder splits a token into its header, payload and signature and shows the decoded claims, converting exp and iat timestamps into readable dates. It runs in your browser, so live tokens are never transmitted.
A JWT decoder answers the question that comes up whenever authentication misbehaves: what does this token actually say? A JWT is three Base64URL segments separated by dots — header, payload and signature — and the payload holds the claims your API is acting on.
The expiry claim is usually the reason you are looking. exp and iat are Unix timestamps, so a raw payload tells you nothing useful; shown as dates it is immediately obvious whether a token has expired, which explains most sudden 401 responses.
Decoding is not verification. Anyone can read a JWT payload, which is why tokens must never carry secrets, and why a decoded token proves nothing about authenticity — only the signature does, and checking it requires the signing key. Because this runs in your browser, pasting a live token does not transmit it anywhere.
How to use the JWT Decoder
- Paste your token. Enter the full JWT including all three dot-separated segments.
- Read the header. Check the signing algorithm and any key ID.
- Read the payload. Inspect the claims, with exp and iat shown as dates.
- Check the expiry. Confirm whether the token is still valid.
JWT Decoder features
- JWT token decoding
- Header payload analysis
- Expiration checking
- Timestamp formatting
- Claim identification
- Security focused
- API debugging support
- Professional accuracy
- Authentication analysis
- Development essential
Frequently asked questions
How does JWT decoding work?
Our decoder splits JWT tokens into three parts: header (algorithm and token type), payload (claims and data), and signature. Uses Base64URL decoding to parse JSON content without cryptographic verification for analysis and debugging.
What JWT components can be decoded?
Complete decoding of: header (alg, typ, kid), payload (iss, sub, exp, iat, jti claims), and signature display. Shows timestamps, expiration status, user information, and token metadata for comprehensive analysis.
Is JWT decoding secure for sensitive data?
Decoding is safe for analysis but doesn't verify signature authenticity. Never trust decoded claims without signature verification. Use for debugging, development, and educational purposes only - not for production security decisions.
What are common JWT claims and their meanings?
Standard claims: iss (issuer), sub (subject), aud (audience), exp (expiration), iat (issued at), jti (JWT ID), and custom claims. Our decoder identifies and formats these claims with human-readable explanations.
How can JWT decoding help with API debugging?
Essential for debugging: inspect token contents, verify expiration times, check user claims, analyze token structure, troubleshoot authentication issues, and understand API authorization mechanisms during development and testing.
What are the limitations of JWT decoding?
Important limitations: no signature verification, cannot validate token authenticity, doesn't check issuer or audience claims, and should not be used for security decisions. Always verify tokens server-side in production.
Is this suitable for professional development?
Absolutely! Professional-grade JWT decoder suitable for developers, security engineers, and API specialists. Perfect for debugging, development, testing, and understanding JWT token structure and contents.