What is a JWT Generator?
A JWT generator builds a signed JSON Web Token from a header, payload, and secret key, encoding each part as base64url and signing the result with HMAC-SHA256. It's useful for testing authentication flows or understanding how JWTs are constructed.
How to Use This JWT Generator
- Edit the header and payload JSON as needed.
- Use the claim shortcut buttons to quickly add sub, iss, exp, iat, or aud.
- Enter a secret key.
- Click Generate JWT to produce the signed token.
- Copy the result with Copy JWT.
When Do You Need a JWT Generator?
This is useful when testing an API that expects a JWT, debugging an authentication integration, or learning how the three parts of a JWT — header, payload, and signature — fit together.
Frequently Asked Questions
When to use JWTs?
JWTs are useful when you need a stateless, self-contained token that carries claims like user ID and permissions, letting a server verify the token without a database lookup — common in API authentication and single sign-on.
JWT signing algorithms?
Common algorithms include HS256 (HMAC with a shared secret), RS256 (RSA with a public/private key pair), and ES256 (elliptic curve). This tool generates HS256 tokens, the simplest and most widely supported option.
How to validate a JWT?
To validate a JWT, recompute the signature using the same secret (or public key) and algorithm, then compare it to the signature in the token. You should also check the exp claim to confirm the token hasn't expired.
JWT vs session cookies?
JWTs are self-contained and don't require server-side storage, making them easy to scale across stateless services. Session cookies require a server-side store but are easier to revoke instantly, since the server controls the session record directly.