JWT Builder
Create, sign, and verify JSON Web Tokens with HMAC algorithms using the Web Crypto API.
What is a JWT Builder?
A JWT builder creates and signs JSON Web Tokens for testing and development. You can define custom header and payload claims, set expiration times, and sign tokens using HMAC-SHA256, HMAC-SHA384, or HMAC-SHA512 algorithms. The builder uses the Web Crypto API for client-side signing — your secret key never leaves your browser.
Common Use Cases
- •Creating test tokens for API development and debugging
- •Building JWTs with specific claims for integration testing
- •Generating tokens with custom expiration for testing auth flows
- •Learning how JWT signing and verification works
- •Creating sample tokens for API documentation
Frequently Asked Questions
Is it safe to sign JWTs in the browser?
For development and testing, yes. The signing happens entirely client-side using Web Crypto API. However, in production applications, JWTs should be signed on the server where the secret key is securely stored.
What claims should a JWT include?
Common claims are: iss (issuer), sub (subject/user ID), exp (expiration time), iat (issued at), aud (audience), and custom claims like roles or permissions. At minimum, always include exp to prevent tokens from being valid forever.