What is JWT Debugger?
JSON Web Tokens (JWTs) are compact, URL-safe tokens used for securely transmitting information between parties. A JWT consists of three parts: a header (specifying the algorithm), a payload (containing claims like user ID, expiration time, and custom data), and a signature (ensuring the token hasn't been tampered with). JWTs are widely used for authentication in modern web applications, mobile apps, and APIs. Our JWT Debugger allows you to decode, inspect, and debug JWT tokens without sending them to any server - a critical security feature when working with production tokens containing sensitive information.
Why Use This Tool?
When debugging authentication issues, you need to inspect JWT contents quickly and safely. Unlike jwt.io which sends your tokens to their servers for decoding, GetDevUtils JWT Debugger runs 100% in your browser. This is essential when working with: production tokens containing user data, tokens from enterprise SSO systems, tokens with sensitive claims like permissions or API keys, and any scenario where token exposure could be a security risk. Our tool also provides enhanced features like automatic expiration checking, claim explanations, and timestamp conversion to human-readable dates.
How to Use JWT Debugger
- Paste your complete JWT token (starting with "eyJ...")
- The tool instantly decodes and displays the header and payload
- Expiration (exp) and issued-at (iat) timestamps are converted to readable dates
- Claims are color-coded: standard claims in blue, custom claims in green
- Expired tokens are clearly marked with a warning indicator
- Copy individual claims or the entire decoded payload as JSON
Features
- Instant decoding with no server communication
- Automatic expiration status checking
- Timestamp conversion to local timezone
- Support for all standard claims (iss, sub, aud, exp, nbf, iat, jti)
- Base64URL decoding with proper handling of padding
- JSON syntax highlighting for payload content
- One-click copy for individual claims
- Token structure validation and error detection
- Clear header algorithm display (HS256, RS256, ES256, etc.)
Common Use Cases
- Authentication Debugging: Verify token contents when login issues occur
- API Development: Inspect tokens during OAuth/OIDC integration
- Security Audits: Review token claims without server exposure
- Mobile Development: Debug tokens from Firebase, Auth0, or Cognito
- Session Management: Check token expiration and refresh timing
Tips & Best Practices
- ✓ Check the "exp" claim immediately when debugging auth failures
- ✓ Compare "iat" (issued at) with current time to detect clock skew
- ✓ Look for "aud" (audience) mismatches in multi-service architectures
- ✓ Verify the algorithm in the header matches your verification setup
How It Compares to Alternatives
jwt.io is the most popular JWT debugger but sends tokens to Auth0's servers. GetDevUtils JWT Debugger processes everything locally, making it the safer choice for production tokens. While jwt.io allows signature verification with a secret, our tool focuses on secure decoding - for signature verification, use our separate JWT Verifier tool which also runs locally.
Frequently Asked Questions
How do I decode a JWT token online?
To decode a JWT token, simply paste the full token into the JWT Debugger input field. The tool instantly decodes the Base64URL-encoded header and payload, displaying the JSON contents in human-readable format. Our JWT decoder online works entirely in your browser without sending tokens to any server.
How can I check JWT token expiration?
Paste your JWT into the debugger, and the tool automatically highlights the exp (expiration) claim in the payload section. We convert the Unix timestamp to a readable date/time format so you can instantly see if the token is expired or still valid.
Is it safe to decode JWT tokens online?
Yes, when using GetDevUtils JWT Debugger! Our tool runs 100% client-side in your browser — your JWT tokens never leave your device and are never uploaded to our servers. All decoding happens locally using browser JavaScript APIs.
Ready to Get Started?
Use JWT Debugger for free - no registration required.
Launch JWT Debugger