By the way, here’s the data you asked me to keep: “user: 12,398,641,238”.Now, the next time you visit any site that happens to use the Facebook pixel, your browser will request: Here’s your pixel.png, and here’s a little bit of data I want you to keep for me: “user: 12,398,641,238”.If you’ve never visited Facebook before (or you’ve just cleared cookies), the request is still: In Ask Leo!’s case, for example, this cookie might include the fact you’re signed in to your Ask Leo! account and don’t need to sign in again every time you move from page to page.Ĭookies apply to images as well - including the Facebook pixel. I’m just using a random number as an example - it could be any data. By the way, here’s the data you asked me to keep last time: 1,860,012,375.Hey ! Could I get “best-articles-collection” from you, please?.The next time you visit any page on that site, the request looks like: Sure, here’s the page, and here’s a little bit of data I want you to keep for me: 1,860,012,375.CookiesĬookies are nothing more than bits of data placed on your computer by websites that are included in subsequent requests when you visit any page on that website again. That’s still not tracking, though it’s just notification. Let’s visit again.įacebook learned a couple of things from this exchange. Then, when the browser discovers that the page includes a reference to the image: It’s called the “ referrer“, or referring page.įor example, for the image at the top of this page, the request is more like: Whenever a browser requests an image to be displayed on a webpage, it includes the URL of the webpage containing the request. So, how does one silly little pixel let Facebook track you? Referrers Hey, ! Could I get “whatever/pixel.png” from you, please?.On the resulting page, the browser finds instructions to “display” the image that is the Facebook pixel, and thus asks: Hey, ! Could I get “some-random-page” from you, please?.That means when you visit a webpage of some random site - I’ll use as my example - your browser says something to the effect of: It’s exactly what it sounds like: a single-pixel image (often invisible) referenced somewhere on the page. Many sites with a Facebook presence - like Ask Leo! has its Facebook Page - are encouraged by Facebook to add what’s called a tracking pixel or Facebook pixel. So what does that have to do with Facebook? So knows you fetched a page, and it knows you fetched an image. Hey, ! Could I get “wp-content/uploads/2021/11/keyhole-spy-2048×” from you, please?. It finds instructions on the page that an image is required, so it then also asks: Hey, ! Could I get “how-does-facebook-track-me-even-if-i-dont-have-an-account” from you, please?.So when you display this page, in addition to the browser saying: (Details of that URL may change due to caching, but the concept remains the same.) For example, when this page is displayed, your browser finds an instruction to display an image, which is then fetched from this location: When an image is displayed - be it in email or on a website - it has to be fetched from somewhere. It’s one of the reasons email programs generally disable images by default. This same technology is also used by advertising networks and others for similar purposes. Because many websites use Facebook-supplied tracking technology, including the “Facebook pixel”, it’s easy for Facebook to collect information about your activities whether you have a Facebook account or not.
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