For forms that should stay human
Protection that does not watch the visitor.
Add one script tag and a site key. The browser does a short calculation in the background. There is no puzzle, no cookie, and no account with a third party.
Try it on a message
This demo checks the proof, then discards the text. Nothing is stored.
Hosted. Your server makes one call to verify the token.
Offline. Or verify it yourself with the published public key, and take no runtime dependency.
Quiet. People are not asked to pick photographs. The hard cases come later, and they stay accessible.