The anti-spam check

On by default for Advanced workflows, with nothing to set up: no key to obtain, no account to create, and no domain to register anywhere.

Protect submissions from spam bots works on whatever domain you publish your form to, from the moment you publish it.

Your visitors see nothing. When someone starts filling in your form, their browser quietly works on a short puzzle Webtzm gives it and sends the answer along with the submission. It normally finishes long before they press send. A visitor who submits immediately may briefly see Finishing a quick anti-spam check… and then their submission goes through as usual.

What it does

It makes automated bulk sending expensive: every submission costs the sender real computing time, which is what makes sending thousands of them impractical.

What it does not do

It is not a bot detector and will not stop a determined, well-resourced sender. Your allowed domains and your monthly submission limit are what cap who can reach your form and how much they can send, and both apply whether this setting is on or off.

Turning it off

Removes the check and nothing else. Consider it if your form sits behind your own login, or if your visitors use browsers old enough to lack modern security features.