Facebook Pixel Tracks You Around the Internet to Serve You Ads
The Facebook pixel is a piece of code that brands add to their website. It’s Facebook’s way of tracking every single visitor’s interactions with the site.
Pixels make ads more effective because they allow Facebook to target users who are already interacting with the brand’s site, or users who are similar to them.
Based on your site behavior, personal details, and whether you bought something, Facebook gets a better idea of other people to show ads to, to maximize spending.
When the pixel code (provided by Facebook) runs on the brand’s website, it does two things:
1) It sends a bunch of information about what you’re doing and looking at on the page, up to Facebook
2) It stores a unique identifier (a cookie) in your browser.
From then on, every time you visit Facebook or sites that use parts of Facebook’s infrastructure (like Facebook login or Facebook Like buttons), the browser will pass the cookie along and Facebook is able to link the activity on those sites back to you. (If you’re interested, the reason it’s called a “pixel” is that it makes a request for an invisible, 1-pixel image from Facebook). All this data goes into a giant machine learning algorithm that spits out ever more accurate predictions of your propensity to buy certain items.
If you’ve ever gone to the website for a cool new shoe brand, and seen ads for it show up on your Instagram stories later, that’s because the store was using a tracking pixel. And Facebook knows that the most likely people to buy these shoes are the people who were looking at them in the first place.
The upshot of all this is that if you’re running ads on Facebook, the pixel is your best friend. If you’re a privacy minded consumer, not so much.
PS: Facebook isn’t the only company to use pixels: Snapchat, Pinterest, Amazon, Google, all have their own. There’s an entire ecosystem on the internet dedicated to showing you relevant ads that will trigger you to spend money. Pixels are at the very heart of our modern advertising landscape.
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For more color, you can check some discussion on Hacker News or Mindstream Media Group. Julia Evans wrote a great blog post looking at tracking as she browsed the internet. Also, here’s a helpful video explaining these pixels.