JWT Debugger
Decode, analyze, and validate JSON Web Tokens with complete privacy. Check token expiration, inspect claims, verify signatures, and debug authentication issues with client-side processing.
💡 This tool has helped 455 users this month
Start Debugging JWT Tokens
Paste your JWT token to decode and analyze its contents instantly
JWT Token Input
🔒 Security Features
- 100% Client-Side: Your tokens never leave your browser
- No Data Storage: Nothing is saved or logged
- Signature Verification: Optional HMAC validation
- Expiration Checking: Automatic exp/nbf validation
- Standard Claims: Recognizes iss, sub, aud, exp, nbf, iat, jti
How to Use JWT Debugger
- 1
Paste Your JWT Token
Copy your JWT token from your application, API response, or authentication header and paste it into the token input field. The tool will automatically detect the token format.
Tip:JWT tokens typically start with 'eyJ' and contain three parts separated by dots (header.payload.signature). - 2
Automatic Token Decoding
The tool instantly decodes your JWT and displays the header and payload in readable JSON format. You can see all claims, metadata, and token structure.
Tip:The signature remains encoded for security - only the header and payload are decoded as they contain non-sensitive metadata. - 3
Verify Token Details
Check token expiration (exp), issued at (iat), issuer (iss), and other important claims. The tool highlights expired tokens and validates token structure.
Tip:Pay special attention to 'exp' (expiration) and 'nbf' (not before) claims to understand token validity timeframe. - 4
Signature Verification
If you have the secret key or public key, you can verify the token's signature to ensure it hasn't been tampered with and is authentic.
Tip:Never paste production secret keys into online tools. Use this feature only with development or test keys.
Security & Privacy
- Decoding runs entirely in your browser; tokens aren’t uploaded.
- Do not paste secrets or production tokens into shared devices.
- Verification depends on the provided key; keep it secure.
Features & Benefits
Instant Token Decoding
Automatically decode JWT tokens to view header and payload content in readable JSON format with syntax highlighting.
Expiration Checking
Instantly see token expiration status and time remaining with visual indicators for expired or soon-to-expire tokens.
Signature Verification
Verify token authenticity by checking signatures with secret keys (HS256) or public keys (RS256) for development tokens.
Claims Analysis
Examine all standard and custom claims including user roles, permissions, issuer, audience, and application-specific data.
Algorithm Support
Support for multiple JWT algorithms including HS256, HS384, HS512, RS256, RS384, RS512, and ES256 for various use cases.
Privacy-First Processing
100% client-side processing ensures your JWT tokens and secret keys never leave your browser for maximum security.
Frequently Asked Questions
Is it safe to paste JWT tokens here?
All JWT processing happens entirely in your browser - tokens are never sent to our servers. However, avoid pasting production tokens with real user data. Use development or test tokens when possible.
What information can I see in a JWT token?
You can see the header (token type and signing algorithm), payload (claims like user ID, expiration, roles, permissions), and verify the signature if you have the secret key.
Why can't I see the signature content?
The signature is a cryptographic hash that verifies token authenticity. It's not meant to be decoded - only verified using the secret key or public key.
What does token expiration mean?
The 'exp' claim shows when the token expires as a Unix timestamp. Expired tokens should be rejected by your application and require the user to re-authenticate.
Can I verify the token signature?
Yes, if you have the secret key (HS256/HS384/HS512) or public key (RS256/ES256). Enter the key in the verification section, but never use production keys in online tools.
What are the most important JWT claims to check?
Key claims include: 'exp' (expiration), 'iat' (issued at), 'sub' (subject/user ID), 'iss' (issuer), 'aud' (audience), and any custom claims specific to your application.
Technical Specifications
Use Cases & Applications
API Authentication Debugging
Debug API authentication issues by examining JWT tokens from authorization headers to understand why requests are failing or being rejected.
Token Expiration Analysis
Quickly check if JWT tokens have expired or will expire soon, helping diagnose authentication timeout issues in applications.
Claims and Permissions Inspection
Examine user roles, permissions, and custom claims embedded in JWT tokens to understand access control and authorization logic.
Integration Testing
Validate JWT tokens generated by authentication services during integration testing to ensure correct claim structure and values.
Third-Party Token Analysis
Analyze JWT tokens from OAuth providers, SSO services, or third-party APIs to understand their structure and extract user information.
Learning and Education
Students and developers learning about JWT tokens can use this tool to understand token structure and see how different claims work.