The Electronic Frontier Foundation (EFF) today announced that its free browser extension Privacy Badger has passed 1 million users. This figure accounts for the three platforms the tool is available for: Google Chrome, Mozilla Firefox, and Opera.

Privacy Badger was first released as an alpha version in May 2014. Its main purpose is to block ads and third-party trackers that do not respect the Do Not Track setting in a user’s browser.

Not blocking these scripts means they can follow you around the web and spy on your browsing habits. The EFF explains how Privacy Badger handles this security and privacy issue:

Third-party tracking — that is, when advertisers and websites track your browsing activity across the web without your knowledge, control, or consent — is an alarmingly widespread practice in online advertising. Privacy Badger spots and then blocks third-party domains that seem to be tracking your browsing habits (e.g. by setting cookies that could be used for tracking, or by fingerprinting your browser). If the same third-party domain appears to be tracking you on three or more different websites, Privacy Badger will conclude that the third party domain is a tracker and block future connections to it.

Privacy Badger always tells how many third-party domains it has detected and whether or not they seem to be trackers. Further, users have control over how Privacy Badger treats these domains, with options to block a domain entirely, block just cookies, or allow a domain.

There is an important line between ad blockers and Privacy Badger, Ghostery, or Firefox’s Tracking Protection feature. While the latter group do end up blocking many ads, they are considered privacy tools because ads that don’t track you are allowed through.

EFF developed Privacy Badger to encourage that advertisers treat users anonymously rather than follow “the industry status quo of online tracking.” If a domain respects the EFF’s Do Not Track policy, which states that the site will not retain any information about users who have expressed that they do not want to be tracked, it is not blocked. You can support the tool’s development with a donation.