What is an ad blockerĪn ad blocker is a browser extension that prevents browsers from loading video and displaying advertisements, pop-ups, tracking pixels and other third-party scripts.Īd blockers not only improve the online experience by hiding ads, but also protect browsing activity from being tracked by third-party scripts. We hope shining a light on this cutting edge technique will be useful to the open source community at large. As the developers of the largest open source browser fingerprinting library, we have only started including ad blocker signals as of April 2021, so this work is hot off the press from our team. While browser fingerprinting is a proven-out method of visitor identification (you can read more about how it works in our beginner’s guide), how ad blockers can be used for fingerprinting is rarely discussed. This combining of browser signals to create a unique identifier is known as browser fingerprinting. These discrepancies provide a source of entropy that when combined with other unique signals, can identify a specific user over multiple visits. By testing whether certain page elements are blocked, a site can find discrepancies in the filters used by your specific ad blocker(s). If you are reading this article on ad blocker technology, you almost undoubtedly have one installed.Īd blockers leave a trace that can be harnessed by the websites you visit to identify you. Around 26% of Americans use an ad blocker today. This novel browser fingerprinting method, while oft-discussed as a theoretical source of entropy, has only just been added to Fingerprint as of April 2021, and has never been fully described until now.Īd blockers are an incredibly pervasive and useful piece of technology.

In this article, we show how signals generated by the use of an ad blocker can improve browser fingerprinting accuracy. Editor's note: we have made some changes to the article introduction for tone and clarity.

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