How Privacy Badger Works

Privacy Badger is a free browser extension made by the Electronic Frontier Foundation (EFF) that stops companies from spying on you online. It works differently from most ad blockers: instead of relying on a fixed list of known bad domains, it watches how third parties behave as you browse and blocks the ones that appear to be tracking you across sites. You install it, and it largely configures itself — no blocklists to maintain and no manual rules required for it to start working.

The core mechanism: behavior, not blocklists

Most blocking extensions ship with a list of domains to block. Privacy Badger instead learns from observed behavior. As you browse, it watches third-party domains that your browser contacts and looks for signs that a given third party is tracking you across multiple, unrelated sites. When a domain appears to be tracking you, Privacy Badger blocks it.

This is why the extension can catch trackers that a static list might miss, and why its behavior can differ from one user to another — what gets blocked depends on what your browser actually encounters.

What counts as a third-party tracker

A third party is a domain that isn't the site you deliberately visited. If you go to example.com and your browser also loads resources from tracker.net, then tracker.net is a third party. Privacy Badger focuses on these third parties and asks whether they appear to be tracking you across the sites you visit.

What about tracking by the site you actually visit

Privacy Badger is built around third-party tracking. It does not treat the site you actively visit — for example, a news site or a social network you navigated to on purpose — the same way it treats an unrelated third party, because that first party already knows you're there. The extension's job is to limit other companies from following you around, not to block the site you chose to open.

The red, yellow, and green sliders

Privacy Badger's menu shows a slider for each third-party domain it has seen. The color tells you what the extension currently thinks about that domain:

The yellow state is a middle ground: rather than breaking a site by blocking a domain outright, Privacy Badger blocks the cookies that domain tries to set while still letting its content load. You can move any slider yourself if you want to allow or block a specific domain, but you don't have to — the extension adjusts these automatically as it learns.

Does it need manual configuration?

For everyday use, no. Privacy Badger starts learning as soon as it's installed and blocks trackers on its own. The main reasons you'd touch the settings are:

• A site breaks. If blocking a domain stops a page from working, you can move that domain's slider to green to allow it.
• You want to see what's happening. The menu shows every third party and its current state, so you can review and override decisions.
• You run a site that gets blocked. The FAQ includes guidance for domain owners who want to stop Privacy Badger from blocking them.

Related capabilities

Beyond the slider-based blocking, Privacy Badger also handles a few specific cases:

• Social media widgets. It can replace embedded social widgets with a placeholder so the social network doesn't see you until you choose to interact.
• Global Privacy Control (GPC). It can send a GPC signal telling sites not to sell or share your data.
• Fingerprinting. It takes steps to reduce fingerprinting, the practice of identifying you by the unique characteristics of your browser.

Getting it

Privacy Badger is available for Chrome, Firefox (including Firefox for Android), Edge (including Edge for Android), Opera, and Brave. If your browser isn't listed, the site notes that it isn't supported there and points to alternative installation options. The extension is made by EFF, a digital rights nonprofit, and its source code is available.