JWT Decoder
Decode and inspect JSON Web Tokens to view header, payload, and expiration status
What is JWT Decoder?
JWT Decoder is a free online tool that decodes JSON Web Tokens to inspect their header, payload, and signature. JWTs are widely used for authentication and authorization in web applications, containing claims like user identity, roles, and token expiration. This tool instantly parses the three parts of a JWT (header, payload, signature), displays the decoded JSON with proper formatting, and shows the token's expiration status. It helps developers debug authentication issues, verify token contents, and understand JWT structure. All decoding happens in your browser, so sensitive tokens are never transmitted to any server.
How to Use
- Paste your JWT token in the input area.
- The header and payload will be automatically decoded and displayed.
- The expiration status is automatically checked.
Tips & Best Practices
- Check the 'exp' claim to quickly verify if a token has expired.
- Compare the 'iat' (issued at) and 'exp' (expiration) timestamps to understand the token's lifetime.
- Inspect the header's 'alg' field to verify the signing algorithm used.
- Never share JWTs in public as they contain sensitive claims that anyone can decode.
- Use this tool to verify that your backend is including the correct claims in issued tokens.
Use Cases
Authentication Debugging
Decode access tokens to verify claims like user ID, roles, and permissions.
Token Inspection
Check if tokens are expired, about to expire, or contain expected claims.
API Development
Verify that your authentication server issues tokens with the correct structure.
Security Audit
Inspect JWTs to ensure sensitive information is not unnecessarily included.
FAQ
What is a JWT?
JWT (JSON Web Token) is a compact, URL-safe token format used for securely transmitting information between parties as a JSON object.
Is it safe to decode JWTs here?
Yes, all decoding happens entirely in your browser. No data is sent to any server.
What is JWT?
JWT (JSON Web Token) is a token format for securely transmitting information between systems, consisting of three parts: header, payload, and signature.
Is my JWT sent to any server?
No, all decoding is performed locally in your browser, so your token information is never exposed externally.
What is the difference between JWT decoding and verification?
Decoding reads the Base64-encoded payload, while verification checks whether the signature is valid using a secret key. This tool only performs decoding.
How can I check a JWT's expiration time (exp)?
The exp claim in the payload is in Unix timestamp format. This tool automatically converts it to a human-readable date and indicates whether the token has expired.
Is my data collected?
No, all decoding happens in your browser. No token data is sent to any server.
Can this tool verify JWT signatures?
This tool decodes the token contents but does not verify signatures, as that requires the signing secret or public key.
What are JWT claims?
Claims are key-value pairs in the payload like 'sub' (subject), 'exp' (expiration), 'iat' (issued at), and custom claims.
Is it safe to decode JWTs in the browser?
Yes, JWT payloads are only Base64-encoded (not encrypted), so decoding reveals information that is already accessible to anyone with the token.
What is the difference between JWT and session cookies?
JWTs are self-contained tokens with claims, while session cookies reference server-side session data. JWTs are stateless.
Why does my JWT show as expired?
The 'exp' claim is a Unix timestamp. If the current time exceeds this value, the token is expired. Check your server's token lifetime settings.