If you wonder why you keep seeing the same ad, over and over, the answer could be fingerprinting.

What is fingerprinting?

Fingerprinting is a type of online tracking that’s more invasive than ordinary cookie-based tracking. A digital fingerprint is created when a company makes a unique profile of you based on your computer, software, add-ons, and even preferences. Your settings like the screen you use, the fonts installed on your computer, and even your choice of a web browser can all be used to create a fingerprint.

If you have a commonly used computer or phone, it may be harder to uniquely identify your device through fingerprinting. However, the more unique add-ons, fonts, and settings you have, the easier you’ll be to find. Companies can use this unique combination of information to create your fingerprint.

Fingerprinting is bad for the web

The practice of fingerprinting allows you to be tracked for months, even when you clear your browser storage or use private browsing mode — disregarding clear indications from you that you don’t want to be tracked. Despite a near complete agreement between standards bodies and browser vendors that fingerprinting is harmful, its use on the web has steadily increased over the past decade.

Firefox blocks fingerprinting

The latest Firefox browser protects you against fingerprinting by blocking third-party requests to companies that are known to participate in fingerprinting. We’ve worked hard to enable this privacy protection while not breaking the websites you enjoy visiting. (Read more here, if you want the technical details.)

And it’s not a deep setting you need to dig around to find. In the latest Firefox browser, fingerprint blocking is the standard, default setting. Visit your privacy protections dashboard to see who’s trying to track you behind the scenes and how Firefox stops them.

You probably wouldn’t appreciate someone tracking your moves in real life. There’s no reason to accept it online. If you don’t already have Firefox, click here to download and protect yourself from digital fingerprinting.

Note: This post was updated in January 2020.

Also published on Medium.

This post is also available in: Deutsch (German) Français (French)