Does my secret leave the browser?

No. Signing uses the browser’s Web Crypto API on your device; the secret is never uploaded and is not saved.

Why only HS256/384/512?

HMAC algorithms sign with a shared secret, which works fully client-side. RS/ES algorithms need an asymmetric private key and are out of scope here.

JWT Generator & Signer

Build a JSON Web Token from a custom payload and sign it with HS256, HS384, or HS512 using your secret — all locally via the Web Crypto API. The companion to the JWT debugger: one decodes, this one creates.

How to use JWT Generator & Signer

Choose an HMAC algorithm and edit the payload JSON.
Add iat/exp claims with one click if you need them.
Enter your secret and copy the signed token.

Frequently asked questions

Does my secret leave the browser?: No. Signing uses the browser’s Web Crypto API on your device; the secret is never uploaded and is not saved.
Why only HS256/384/512?: HMAC algorithms sign with a shared secret, which works fully client-side. RS/ES algorithms need an asymmetric private key and are out of scope here.

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