JWT Decoder
Decode and analyze JWT tokens
The JWT Decoder takes a JSON Web Token string and automatically splits it into its three components โ header, payload, and signature โ decoding the Base64 content into readable JSON. It displays claims like expiration time (exp), issued-at (iat), and custom user data at a glance. An essential debugging tool for developers implementing OAuth flows, API authentication, and token-based authorization systems.
๐ How to Use
- Paste a JWT token in the input area
- Header and payload are decoded automatically
- Check expiration time and claims
- View token validity status
โจ Features
- โAutomatic header/payload decoding
- โExpiration time check
- โClaims information display
- โValidity status display
- โJSON formatted output
๐ก Use Cases
- โขBackend Developer: Inspect JWT claims and expiration times when debugging API authentication failures.
- โขFrontend Developer: Verify that login tokens contain the correct user information and roles after authentication.
- โขQA Engineer: Check role and permission claims in tokens during authorization testing across different user types.
- โขSecurity Engineer: Audit tokens to ensure sensitive information isn't exposed in the payload.
- โขStudent: Study JWT structure and understand what each standard claim means using real token examples.
- โขDevOps Engineer: Monitor token expiration settings in service-to-service communication and microservice architectures.
๐ฏ Tips
- โธPaste a token and decoding happens instantly. The 'Bearer ' prefix is automatically stripped if included.
- โธThe exp (expiration) and iat (issued at) fields are Unix timestamps. The tool converts them to human-readable dates automatically.
- โธRemember that JWT payloads are Base64-encoded, not encrypted. Never store passwords or sensitive data in the payload.
- โธIf a token shows as expired, you need to request a new one. Use refresh tokens to maintain seamless authentication.
โ FAQ
Q. Does it verify the signature?
A. This tool only decodes. Signature verification requires the secret key on the server.
Q. What are the three parts of a JWT?
A. Header (algorithm), payload (data), and signature - three parts separated by dots.
Q. Is it safe if the JWT payload is visible?
A. JWT payloads are only Base64-encoded, not encrypted. This means anyone can read the contents. Never include passwords, credit card numbers, or other sensitive data in the payload. The signature only prevents tampering, not reading.
Q. What's the difference between HS256 and RS256?
A. HS256 uses a symmetric key (single shared secret) for signing, while RS256 uses asymmetric keys (public/private key pair). In microservice environments, RS256 is preferred since you only need to distribute the public key for verification.
Q. Why won't my token decode?
A. A valid JWT must have exactly three parts separated by dots (.). Remove any leading/trailing whitespace or line breaks, and verify the complete token was copied. Truncated tokens will fail to decode.