What is a JWT Decoder?
A JWT (JSON Web Token) decoder analyzes JWT tokens by separating them into Header, Payload, and Signature parts, displaying each in human-readable JSON format. JWT is a widely-used standard (RFC 7519) for authentication and information exchange in web applications.
This tool performs Base64Url decoding directly in the browser without any external libraries. It automatically converts token timestamps (exp, iat, nbf) to human-readable dates and checks expiration status in real-time.
Key Features
3-Part Separated Display
Precisely separates JWT tokens into Header, Payload, and Signature parts, displaying each in formatted JSON for easy reading.
Automatic Timestamp Conversion
Automatically converts Unix timestamp values like exp, iat, and nbf to human-readable date/time format.
Expiration Status Display
Compares the token's exp claim with the current time to instantly show Expired or Valid status.
Copy Each Part
Copy Header, Payload, or Signature to clipboard directly for convenient use during development.
Browser-Only Processing
All decoding is performed in the browser, so JWT tokens are never sent to any server. Analyze even security-sensitive tokens with confidence.
How to Use
- Enter JWT Token — Paste the JWT token you want to decode into the input field. You can also try a sample using the 'Sample Token' button.
- View Header — Check the algorithm (alg) and token type (typ) information in the decoded JWT Header.
- Analyze Payload — Review the claims information in the Payload. Timestamps are automatically converted to dates.
- Use Results — Check the expiration status and copy any section to clipboard using the copy button.
Use Cases
API Debugging
Quickly inspect JWT token contents returned from REST APIs to debug authentication issues.
Token Expiration Check
Instantly verify when a JWT token expires and whether it's currently valid to diagnose authentication errors.
Claims Verification
Quickly review user information (sub, name, role, etc.) and permission-related claims contained in the token.
Learning & Education
Visually understand JWT structure and how it works. See firsthand what information each part contains.
Frequently Asked Questions
What is JWT?
JWT (JSON Web Token) is a standard (RFC 7519) for securely transmitting information between parties as a JSON object. It consists of three parts: Header, Payload, and Signature, and is mainly used for authentication and information exchange.
Is it safe to decode a JWT?
JWT Header and Payload are only Base64Url-encoded, not encrypted. Anyone can decode and view the contents. Sensitive information should not be included in the JWT Payload.
What are exp, iat, and nbf?
exp (Expiration Time) is the token expiration time, iat (Issued At) is the token issuance time, and nbf (Not Before) is the start time when the token becomes valid. All are recorded as Unix timestamps (in seconds).
How do I check if a JWT token has expired?
Compare the 'exp' claim in the JWT Payload with the current time. This decoder automatically determines expiration and displays 'Expired' or 'Valid' status.
Is my JWT token stored on the server?
No. This tool performs all decoding in the browser. The JWT token you enter is never sent to any server, and is completely deleted when you close the page.
Privacy Notice
This JWT decoder performs all decoding in your browser. JWT tokens you enter are never sent to any server and are completely deleted when you close the page. Analyze even security-sensitive tokens with confidence.