JWT Signer

JWT Signer is a free encode & crypto tool that runs entirely in your browser — build & HMAC-sign a token. No upload, no account, no limits.

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How to use JWT Signer

Open the JWT Signer tool.
Paste or type your text, code or a token into the input field.
The output updates as you type — adjust the options if you need a different format.
Copy the result, or share the URL to hand the exact input to someone else.

About JWT Signer

Build and HMAC-sign a JSON Web Token from your own payload. Pick HS256, HS384 or HS512, supply the secret key, and the header, signing input and signature are assembled and signed locally with the Web Crypto API.

This produces real, verifiable tokens for testing — keep the secret private, since anyone with it can mint valid tokens.

What people use it for

Mint a test token with specific claims for a local API.
Reproduce a signed token to debug auth middleware.
Experiment with HS256/384/512 signing to learn how JWTs are built.

Frequently asked questions

Which algorithms can it sign with?

HMAC with SHA-256, SHA-384 or SHA-512 (HS256/HS384/HS512), computed via the Web Crypto API.

Is the secret sent anywhere?

No. Signing happens entirely in your browser; the secret never leaves the page.

Is it private?

Every calculation happens on this page, in your own browser. Your input is never sent to a server, never logged and never used for training — which also means the tool keeps working when you are offline.