Definition: Conversion Pixel

A conversion pixel is a 3rd party piece of code placed on a website that allows an advertiser or ad platform to track conversions. Conversion Pixels are typically placed on confirmation pages, but can also be placed on landing pages, or throughout a site.

A conversion pixel is an image file that is 1 pixel tall and 1 pixel wide that is hosted outside of the website being visited. As the pixel is so small, it cannot be seen by the naked eye meaning users don’t notice when they load.

The conversion pixel is hosted on a server used to track ads and therefore every time the pixel is loaded, that server can record it. Other information is sent along with the pixel request from the user’s computer – and this is used to match the user back to advertising.


Example of how a Conversion Pixel works

Here is an example of how a conversion pixel can work. There are many variations of how tracking works, so this is a broad-strokes example only:

  1. Julia clicks on an ad for scarves on Facebook and goes to the advertiser’s website.
  2. Facebook records that Julia clicked on the ad.
    • It can do this in a variety of ways, by recording things such as IP address, device ID, username etc
  3. Julia sees a scarf she like on the advertiser’s website and makes a purchase.
  4. After the sale, Julia is taken to a confirmation page that contains a Facebook conversion pixels code.
  5. The conversion pixel loads from Facebook’s server and the request for the pixel is sent with Julia’s device ID
  6. The device ID is matched by Facebook to the list of people who interacted with the ad.
  7. The advertiser is charged by Facebook for their ad leading to a sale.

There are several things to note about this example:

  • Facebook’s pixel is more complicated than this and can scrape information from a page. It is also typically placed on every page.
  • Pixels often drop cookies, which can also be used to track conversions.
  • The information stored by the ad platform should be anonymized so they can’t tell who you are, only that someone who saw or clicked on the ad converted.
  • Whether or not you interacted with an ad on the original site (Facebook in this case), the pixel is loaded when you make a purchase. This means that your information is sent to the site the ad was on regardless. This is a major reason why people dislike advertising tracking.
  • Ads are often run on multiple websites at the same time, meaning that each purchase can trigger multiple conversion pixels. This in turn means that after any purchase on the internet, many companies that you have never interacted with will be informed. Even if your information is anonymised by all of them, this is obviously far from ideal.


Top Tip

Websites should not drop any cookies or pixels on a users computer unless permission has been given by the user to do so. This is due to cookie regulations in many countries, as well as common decency.

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