Nothing. Here is how to check that yourself.
What follows is your own browser, reporting what this page has actually done while you have been reading it.
Your browser’s own answer, right now
Your browser keeps its own record of every site a page contacts and everything a page saves on your machine. This reads that record back to you. Nothing below left your computer.
Checking…
Three things leave this browser, and only when you ask for them: the domain you type into the test, a question you send to the dialogue at the end, and a message you send through the contact form. Each goes to our own server in Germany, and none of them is written down.