JWT Decoder
Decode and validate JWT tokens instantly. View header, payload, and signature. Check expiration status. Free JWT decoder tool.
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What is JWT Decoder?
JWT Decoder is a tool that decodes JSON Web Tokens (JWT) to reveal their header, payload, and signature. JWTs are compact, URL-safe tokens used for authentication and information exchange in web applications, APIs, and single sign-on systems.
Key Benefits
- Instant decoding
- Shows all token parts
- Expiration checking
- No server required
Common Use Cases
- •API debugging
- •Authentication troubleshooting
- •Token validation
- •Security auditing
How to Decode JWT Tokens
- Paste your JWT token: Copy the complete JWT token (the long string starting with "eyJ...") and paste it into the input field.
- View the decoded parts: The decoder instantly shows three sections: Header (algorithm info), Payload (claims data), and Signature (verification).
- Check token validity: Look for the expiration (exp) claim to see if the token is still valid. Expired tokens will be marked with a warning.
- Copy decoded JSON: Click to copy the header or payload as formatted JSON for use in documentation or debugging.
Key Features
- Decode JWT header, payload, and signature
- Expiration time validation
- Formatted JSON output
- Copy decoded data as JSON
- Identifies signing algorithm
- Client-side only - tokens never transmitted
Frequently Asked Questions
How do I decode a JWT token?
Paste your JWT token into the input field, and the decoder instantly shows the header, payload, and signature. You'll see claims like expiration time (exp), issued at (iat), and the signing algorithm. No secret key is needed to read the payload.
Is it safe to decode JWT tokens online?
For read-only decoding, yes—JWT payloads are Base64 encoded, not encrypted, so the data is visible. However, never enter production tokens containing sensitive data online. Our tool processes everything client-side with no server transmission.
Why can anyone read JWT payload data?
JWT uses encoding (Base64), not encryption. The purpose of JWT is integrity verification (proving the token wasn't modified), not confidentiality. Sensitive data should not be stored in JWT payloads. The signature ensures authenticity, not privacy.
What does it mean when a JWT is expired?
JWTs include an expiration claim (exp) as a Unix timestamp. After this time, the token should be rejected. Expired tokens indicate the user/session needs reauthentication. Short expiration times (15min-1hr) improve security by limiting token theft damage.
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