Does Constructor use third-party cookies to track visitors?

No. Constructor's Javascript beacon uses first-party cookies to track visitors -- that is, the cookie is set on your own domain, not on Constructor's. This provides privacy protection for your users. The cookie is tied only to your domain(s) and there is no way Constructor can link visitor data to your users when they are off your site. Because of this and additional related measures, Constructor's visitor tracking is built to not run afoul of privacy protections offered by modern browsers and is not affected by browsers that block third-party cookies.