JWT Encoder & Signer — Token Builder
Construct and sign JWT tokens locally in your browser. Edit header and payload JSON, choose HS256/HS384/HS512, enter a secret, and generate a signed token instantly. Nothing is uploaded.
How to Use JWT Encoder & Signer — Token Builder
How to Use the JWT Encoder & Signer:
Select Algorithm: Choose HS256 (default), HS384, or HS512. The algorithm is automatically set in the header JSON.
Edit the Header: The header defaults to {"alg":"HS256","typ":"JWT"}. You can add additional fields (e.g., kid for key ID), but the alg field is controlled by the algorithm selector.
Edit the Payload: Enter your claims as a JSON object. Standard claims:
- sub — subject (user ID, service name)
- iat — issued at (Unix timestamp, seconds)
- exp — expiry (Unix timestamp, seconds)
- iss — issuer
- aud — audience Custom claims are also supported as any JSON field.
Enter Your Secret: Type or paste your HMAC signing secret. Use the Show/Hide toggle to reveal it. The secret is only used in your browser and never uploaded.
Click Generate Token: The tool signs the header and payload using the Web Crypto API and displays the signed JWT with colour-coded sections (red = header, purple = payload, cyan = signature).
Copy the Token: Click Copy to copy the full JWT to your clipboard. Use the JWT Token Validator to verify the output.
Notes
- Only HMAC algorithms (HS256, HS384, HS512) are supported. RS256/ES256 require a private key and are not available in the browser.
- The payload is Base64URL-encoded, not encrypted — do not include secrets or sensitive data in the payload.
- Tokens generated here are real, valid JWTs suitable for development and testing.
Frequently Asked Questions
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