Unlike most other privacy tools, Privacy Badger automatically learns what to block over time.
We pre-train Privacy Badger for you so that it already knows about many popular trackers when you first install it. (Visit https://www.eff.org/deeplinks/2018/08/giving-privacy-badger-jump-start to learn more.) But the database isn't fixed: Privacy Badger learns from your browsing.
To get answers to Privacy Badger questions, visit our FAQ (https://www.eff.org/privacybadger/faq), check out our GitHub issue tracker at https://github.com/EFForg/privacybadger/issues, or simply email firstname.lastname@example.org
Edit: To clarify, Privacy Badger starts blocking a domain once it sees that domain perform tracking on three different websites. The idea is to avoid blocking too much, while still protecting your privacy across the Web.