JWT Generator

Overview

• Generates a signed JWT (JSON Web Token) from a Header, Payload, and Secret (signing key) you specify.
• Supports HMAC-based signing algorithms (HS256, HS384, HS512), switching the signing method based on the alg value specified in the Header.
• Signing uses the Web Crypto API and happens entirely in your browser, so the Secret is never sent externally.

Usage

1. Enter JSON data into the Header and Payload fields. Set the Header's alg to HS256, HS384, or HS512.
2. Enter the secret key to sign with into Secret.
3. Click the "Generate" button to display the signed JWT. Use the "Copy" button to copy it to the clipboard.

Example

Header: {"alg":"HS256","typ":"JWT"}
Payload: {"sub":"1234567890","name":"Taro"}
Secret: my-secret

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IlRhcm8ifQ.xxxxx

Use Cases

• Issuing a test JWT on the spot with arbitrary claims (Payload) while implementing or debugging authentication
• Preparing multiple JWTs with different expiration (exp) or role claims to verify API authorization logic
• Generating a token signed with a known Secret for use in unit tests of JWT verification logic

FAQ

Notes

• Only the HMAC-based algorithms HS256, HS384, and HS512 are currently supported. Public-key algorithms such as RS256 are not supported.
• Do not enter a secret key that is actually used in production here. We recommend limiting use to testing and verification.
• Entering invalid JSON into the Header or Payload results in an error.