JWT Generator

What is JWT Generator?

JWT Generator creates signed JSON Web Tokens from custom header and payload JSON with support for HMAC-SHA256, HMAC-SHA384, and HMAC-SHA512 signing algorithms using the Web Crypto API. It lets you set standard registered claims like iss, sub, aud, exp, and iat through form fields, and add custom claims for application-specific data. The tool generates a complete, valid JWT string ready for testing purposes.

Backend developers building authentication systems, QA engineers testing API authorization rules, and security engineers validating JWT handling logic. The tool runs entirely in your browser — your data never leaves your device.

How to Use JWT Generator

1. Select the signing algorithm — HS256, HS384, or HS512 — from the header configuration
2. Fill in the standard claims like issuer, subject, audience, and expiration time
3. Add any custom claims as key-value pairs in the payload section
4. Enter or generate a secret key for HMAC signing
5. Click Generate to produce the signed JWT and copy it for use in API testing

Common Use Cases

• Creating test tokens for local API development without setting up a full auth server
• Generating tokens with specific claims to test API authorization rule enforcement
• Prototyping JWT-based authentication flows before implementing the token issuance service
• Creating tokens with expired or future dates to test expiration handling logic
• Building tokens with custom roles and permissions claims for RBAC testing

Pro Tips

• Set the exp claim a few minutes in the future for test tokens — tokens without expiration are a security risk if accidentally used in production
• Use a strong secret key (256+ bits of randomness) for HMAC signing — a weak secret can be brute-forced, allowing token forgery
• The iat (issued at) claim is automatically set to the current time — verify that your API correctly rejects tokens where iat is in the future

Why Use This Tool?

• Privacy-first: All processing happens locally in your browser. No data is transmitted to any server.
• No installation required: Works in any modern browser on desktop or mobile.
• Completely free: No account, no credit card, no usage caps.
• Fast and reliable: Powered by modern Web APIs for near-instant results.

Related Concepts

Learn more about related topics: HMAC-SHA256, JWS, Bearer token, OAuth 2.0.

Frequently Asked Questions