JWT Generator

How to Use the Free Client-Side JWT Generator

This tool builds fully signed JWTs in your browser, letting you create realistic tokens for testing without standing up a separate signing service. Signing happens locally via the Web Crypto API, so your secret key never travels anywhere.

1. Enter a JSON payload containing standard claims like sub, exp, iat, and iss, plus any custom fields.
2. Provide a strong secret key and choose between HS256, HS384, and HS512.
3. Open the advanced options to customize header parameters such as kid, typ, and cty if you need them.
4. Click Generate, then copy the three-part token for use in your API requests.

When to Use JWT Generator

Authentication debugging is where this tool earns its time. When you need a token with a specific claim set to reproduce a bug, test an expiry edge case, or exercise authorization logic, minting one on demand beats waiting for a real login flow. API developers use it to create fixtures for integration tests, and security testers rely on it to check how their server reacts to tokens with unusual claims or header values.

The customization options matter for single sign-on work. Being able to set issuer, audience, and custom fields in the payload, then tune header parameters like kid, mirrors what real SSO providers emit, so you can validate your verification code against realistic tokens before you ever integrate. Because the tool signs with symmetric HS algorithms, you stay in full control of the secret.

JWT Generator Tips and Best Practices

1. Use at least a 256-bit secret, meaning 32 random bytes, for HS256. Weak secrets can be brute-forced, which lets an attacker forge tokens with arbitrary claims.
2. Always include an exp claim. Tokens without expiration never expire, and a stolen one stays valid forever. Short lifetimes of 15 to 60 minutes dramatically shrink the window for abuse.
3. Treat the generated token as real even though it was made for testing. If it encodes user data, a leaked copy is still useful to an attacker.
4. Keep your test secret distinct from production keys, and store it in your environment configuration, never in source control.

Why Client-Side Privacy Matters for creating signed tokens for authentication testing and development

A JWT generator is only as useful as it is safe to use with real secrets. If the secret key used to sign tokens is sent to a server, it can be logged, leaked, or reused, and anyone holding it can mint valid tokens for your entire system.

Here the entire signing process runs in your browser. The payload and the secret key stay on your device, nothing is uploaded, and the only artifact that leaves your screen is the finished token you copy out.