HTMLJWT Builder
Compose a JWT from scratch — edit the header and payload JSON, choose HMAC-SHA256, and sign with your own secret key. All operations run in-browser using the Web Crypto API. Useful for testing API authentication, debugging token issues, and understanding the JWT format.
Ctrl+Enter to run | Ctrl+K to switch tools | Recent button shows input history
Repeating this work? Turn this kind of browser utility into an API batch, MCP prompt, extension workflow, or shared team recipe.
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Is this safe to use with real secrets?
Yes — signing happens entirely in your browser via the Web Crypto API. Nothing is sent to any server. Treat any generated token as sensitive; don't paste real production secrets into untrusted online tools.
What is a JWT?
A JSON Web Token is a compact, URL-safe string encoding a JSON header, a JSON payload, and a cryptographic signature. The signature lets the server verify the payload hasn't been tampered with.