As part of its Enhanced Tracking Protection feature, Mozilla is planning on blocking Fingerprinters by default in Firefox 72, which is slated to be released in January 2020.

Fingerprinters are a tracking method that allows a company to track you based on characteristics of your computer rather than through tracking cookies.

It does this by building a profile of your device based on its characteristics such as the screen resolution, the browser you use, timezone, language, installed extensions, the installed fonts, and your operating system.