Firefox has been offering a "Do Not Track" option for quite a while (under Tools / Options / Privacy ).  The problem is that websites were not required to honor that request.

Firefox has now added an new feature, called "Tracking PROTECTION", which uses a blocklist to actively block domains and sites that are known to track users.

For details --- including how to activate this feature --- see https://finance.yahoo.com/news/firefox-helps-cover-assets-latest-174857917.html