Firefox does not have a built-in ad blocker. The "Tracking content" blocking through the Tracking Protection feature will prevent some ad server scripts from running, so indirectly, some ads will be blocked that way. Since the shield icon at the left end of the address bar in your screenshot is a bit purplish, ''something'' is being blocked already, but you could adjust your protection level and see whether that makes any difference. More info: [[Enhanced Tracking Protection in Firefox for desktop]]. By the way, if you click that little "Why ads?" link, does it say anything about them that would provide more information?