Today we are introducing Badger Swarm, a new tool for Privacy Badger that runs distributed Badger Sett scans in the cloud. Badger Swarm helps us continue updating and growing Privacy Badger’s tracker knowledge, as well as continue adding new ways of catching trackers. Thanks to continually expanding Badger Swarm-powered training, Privacy Badger comes packed with its largest blocklist yet.

A line chart showing the growth of blocked domains in Privacy Badger’s pre-trained list from late 2018 (about 300 domains blocked by default) through 2023 (over 2000 domains blocked by default). There is a sharp jump in January 2023, from under 1200 to over 1800 domains blocked by default.

We continue to update and grow Privacy Badger’s pre-trained list. Privacy Badger now comes with the largest blocklist yet, thanks to improved tracking detection and continually expanding training. Can you guess when we started using Badger Swarm?

Privacy Badger is defined by its automatic learning. As we write in the FAQ, Privacy Badger was born out of our desire for an extension that would automatically analyze and block any tracker that violated consent, and that would use algorithmic methods to decide what is and isn’t tracking. But when and where that learning happens has evolved over the years.

When we first created Privacy Badger, every Privacy Badger installation started with no tracker knowledge and learned to block trackers as you browsed. This meant that every Privacy Badger became stronger, smarter, and more bespoke over time. It also meant that all learning was siloed, and new Privacy Badgers didn’t block anything until they got to visit several websites. This made some people think their Privacy Badger extension wasn’t working.

In 2018, we rolled out Badger Sett, an automated training tool for Privacy Badger, to solve this problem. We run Badger Sett scans that use a real browser to visit the most popular sites on the web and produce Privacy Badger data. Thanks to Badger Sett, new Privacy Badgers knew to block the most common trackers from the start, which resolved confusion and improved privacy for new users.

In 2020, we updated Privacy Badger to no longer learn from your browsing by default, as local learning may make you more identifiable to websites. 1 In order to make this change, we expanded the scope of Badger Sett-powered remote learning. We then updated Privacy Badger to start receiving tracker list updates as part of extension updates. Training went from giving new installs a jump start to being the default source of Privacy Badger’s tracker knowledge.

Since Badger Sett automates a real browser, visiting a website takes a meaningful amount of time. That’s where Badger Swarm comes in. As the name suggests, Badger Swarm orchestrates a swarm of auto-driven Privacy Badgers to cover much more ground than a single badger could. On a more technical level, Badger Swarm converts a Badger Sett scan of X sites into N parallel Badger Sett scans of X/N sites. This makes medium scans complete as quickly as small scans, and large scans complete in a reasonable amount of time.

Badger Swarm also helps us produce new insights that lead to improved Privacy Badger protections. For example, Privacy Badger now blocks fingerprinters hosted by CDNs, a feature made possible by Badger Swarm-powered expanded scanning. 2

We are releasing Badger Swarm in hope of providing a helpful foundation to web researchers. Like Badger Sett, Badger Swarm is tailor-made for Privacy Badger. However, also like Badger Sett, we built Badger Swarm so it's simple to use and modify. To learn more about how Badger Swarm works, visit its repository on GitHub.

The world of online tracking isn't slowing down. The dangers caused by mass surveillance on the internet cannot be overstated. Privacy Badger continues to protect you from this pernicious industry, and thanks to Badger Swarm, Privacy Badger is stronger than ever.

To install Privacy Badger, visit Thank you for using Privacy Badger!

  • 1. You may want to opt back in to local learning if you regularly browse less popular websites. To do so, visit your Badger’s options page and mark the checkbox for learning to block new trackers from your browsing.
  • 2. As a compromise to avoid breaking websites, CDN domains are allowed to load without access to cookies. However, sometimes the same domain is used to serve both unobjectionable content and obnoxious fingerprinters that do not need cookies to track your browsing. Privacy Badger now blocks these fingerprinters.

Related Issues