Product
What CDPCaptcha does
CDPCaptcha asks the browser for a short proof of work instead of a picture puzzle.
The check uses no cookies and no tracking.
Included
The pieces that make the check.
Each part is there to slow automated abuse without handing the visitor a riddle.
Proof of work
A Web Worker runs a small SHA-256 search in the background.
The person keeps reading while that calculation finishes.
In the browser
No cookies
The widget stores nothing in the browser and does not call a third party.
Rate limits use a salted hash of the address.
No tracking
Signed puzzles
The server signs every puzzle with HMAC-SHA256.
The puzzle expires, and the verification accepts it only once.
Single use
Your server or ours
Install it on your own PHP host, or use the service that is made and hosted in the EU, in Germany.
EU and Germany
Next
Read the detail where it lives.
Developer documentation explains the embed and the verification call.
The cybersecurity wiki explains the threats those controls address.
Try it on your own form
Create a sitekey and put the widget on a page you control.