You have never clicked an ad. You have never signed up for a newsletter. You have never interacted with a brand in any way — and yet, somehow, its adverts follow you around the internet for weeks after you visited its website once.
This is the tracking pixel at work. Here is exactly what it is, how it works and what you can do about it.
What Is a Tracking Pixel?
A tracking pixel (also called a web beacon or pixel tag) is a tiny piece of code — usually a 1×1 transparent image or a JavaScript snippet — embedded in a webpage or email. When you load the page, your browser automatically fetches the pixel from the tracker's server. That fetch request contains your IP address, browser type, operating system, screen resolution, the page you were viewing and a unique identifier linked to your browser profile.
All of this happens invisibly, in milliseconds, before you have interacted with the page at all.
The Facebook Pixel Explained
The most well-known tracking pixel is the Facebook Pixel (now called the Meta Pixel). It is a snippet of JavaScript that website owners embed in their pages. When you visit a site with the Pixel installed, it fires a request to Facebook's servers containing data about your visit — even if you are not logged into Facebook at the time.
Facebook uses this data to build an advertising profile linking your real-world browsing behaviour to your Facebook identity. When the site owner then runs Facebook ads, they can target people who previously visited specific pages, added items to a cart, or completed a purchase. The Pixel is estimated to be present on 30–40% of all websites worldwide.
Other Common Trackers
Beyond Facebook, dozens of tracking networks operate the same way. Google Analytics tracks visits across most of the web. Google Tag Manager loads multiple tracking scripts in one. TikTok, LinkedIn, Twitter/X, Pinterest and Snapchat all have their own pixels. Hotjar and Clarity record your mouse movements and keystrokes in session recordings. Criteo and DoubleClick build retargeting profiles to serve you ads across different sites.
A single news website might load 15–30 different trackers simultaneously. You can check any website using our free Tracker & Pixel Scanner — paste any URL and see exactly which trackers are present.
Why This Matters
Tracking pixels create detailed profiles of your behaviour across websites you have never directly given data to. These profiles include what products you looked at, what articles you read, what health conditions you searched for and what political content you engaged with. This data is sold, shared and used to target you with advertising — and sometimes with more concerning applications.
Tracking pixels in emails are particularly intrusive. When you open an email, the pixel fires and tells the sender your IP address (and therefore approximate location), the time you opened the email and the device you used. This happens even if you do not click anything.
How to Protect Yourself
Browser extensions: uBlock Origin, Privacy Badger and Ghostery block most tracking pixels automatically. uBlock Origin is the most effective — it blocks by default with no configuration needed.
Firefox: Has Enhanced Tracking Protection enabled by default. The Strict setting blocks almost all known trackers.
Brave: Blocks trackers at the browser level with no extensions needed.
DNS-level blocking: NextDNS and Pi-hole block tracking domains for all apps on your network, including apps that cannot use browser extensions.
Email clients: Apple Mail on iOS blocks email tracking pixels by default since iOS 15. In Gmail, images are proxied through Google's servers, which somewhat limits the data advertisers receive.
Check What Trackers Are on Any Site
Want to see exactly what trackers are running on a specific website? Use our free Tracker Scanner — enter any URL and get a full breakdown of analytics, advertising pixels, heatmap scripts, social widgets and retargeting tools present on that page.
