JWT Encoder Decoder
Securely encode, decode, and validate JSON Web Tokens with signature verification
JWT Token Input
Header
{
"alg": "HS256",
"typ": "JWT"
}
Payload
{
"sub": "1234567890",
"name": "John Doe",
"iat": 1516239022
}
Signature
Enter JWT to see signature
Signature Verification
Header
Payload
Encoding Configuration
Generated JWT Token
When to Use JWT Encoder Decoder
API Authentication
Debug and validate JWT tokens used in API authentication. Verify token structure, expiration times, and signature validity for secure API access.
OAuth Integration
Analyze OAuth access tokens and ID tokens. Inspect claims, validate scopes, and ensure proper OAuth 2.0 and OpenID Connect implementation.
Security Testing
Perform security audits on JWT implementations. Test for common vulnerabilities like algorithm confusion, weak signatures, and expired tokens.
Development Debugging
Debug JWT-based authentication in applications. Inspect token contents, verify claims, and troubleshoot authentication issues during development.
Token Analysis
Analyze JWT token structure and claims for compliance audits. Extract user information, permissions, and metadata for security reviews and documentation.
Custom Claims Testing
Create and test JWT tokens with custom claims for specific use cases. Generate tokens with role-based permissions, tenant information, and custom attributes.
Frequently Asked Questions
What is JWT and how does it work?
JWT (JSON Web Token) is a compact, URL-safe means of representing claims between two parties. It consists of three parts separated by dots: Header (contains algorithm and token type), Payload (contains claims/data), and Signature (ensures token integrity). JWTs are commonly used for authentication, authorization, and secure information exchange in web applications and APIs.
Is this JWT decoder tool secure and private?
Yes, our JWT tool processes all tokens entirely within your browser using client-side JavaScript. No JWT data, keys, or sensitive information is transmitted to our servers or any third parties. This ensures complete privacy and security of your confidential tokens and cryptographic keys.
What JWT algorithms and signing methods are supported?
We support all major JWT algorithms including HMAC-based (HS256, HS384, HS512), RSA-based (RS256, RS384, RS512), and ECDSA-based (ES256, ES384, ES512) signing algorithms. You can decode tokens with any algorithm and encode new tokens using your preferred signing method.
How do I verify a JWT signature properly?
To verify a JWT signature: 1) Paste your JWT token, 2) Select the correct algorithm from the dropdown, 3) Enter the appropriate secret key (for HMAC) or public key (for RSA/ECDSA), 4) Click "Verify Signature". The tool will validate the signature and display the verification status with detailed security information.
Can I create and encode new JWT tokens?
Absolutely! Switch to "Encode JWT" mode, edit the header and payload JSON, select your signing algorithm, provide a secret or private key, and click "Encode JWT". The tool generates a properly formatted, signed JWT token ready for use in your applications.
What should I do if my JWT token is expired?
If your JWT shows as expired (current time exceeds the 'exp' claim), you need to request a new token from your authentication server. Expired tokens should never be accepted for security reasons. Our tool will highlight expiration status and time remaining for active tokens.
How can I test JWT security and find vulnerabilities?
Use our tool to test common JWT vulnerabilities: verify signature validation is working, test with modified payloads to ensure tampering detection, check algorithm confusion attacks by changing the 'alg' header, and validate that expired tokens are properly rejected by your application.
Is there a limit on JWT token size or number of operations?
No, our JWT tool has no artificial limits on token size or usage frequency. Since all processing happens locally in your browser, you can work with large tokens, complex payloads, and perform unlimited encode/decode operations without restrictions or rate limiting.
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