What is a Pixel?

A pixel (also known as 1×1 tracker) is a piece of code, which gathers information about visitors. This information is used to report on an advertising campaign’s performance, or to build new segments.

Why is it called a pixel?

Traditionally, a pixel is loaded by inserting an image on a webpage or email. These images are 1 pixel wide and 1 pixel tall. The image is a single pixel.

How are pixels used?

An advertiser places a pixel on a webpage or email. When that pixel is loaded, the visitor’s web browser sends information to the provider of that pixel. Advertisers use tools offered by ad-tech vendors (such as Google or Facebook) to create a pixel.

The advertiser will have a dashboard, where they can see how often that pixel is loaded. This gives the advertiser an idea of how often the measured event has taken place. Using this information, the advertiser can understand their advertising campaign’s performance.

In addition, visitors who loaded that pixel, can be placed into an audience. The advertiser can choose to show ads to this audience again. This is called re-targeting.

How do pixels work?

Pixels tend to be long URLs, for example:

Whenever this URL (the pixel) is loaded, it will measure this as a hit for a given site and marketing campaign.

When the URL is loaded, the following information is sent to the pixel provider:

  • Browser (e.g. iOS Safari 12)
  • Website where the pixel was loaded
  • Screen resolution
  • Time
  • IP address (which can be used to determine location)
  • Cookies

In addition, the pixel provider can “connect the dots.” If a user loads one pixel on Website A and a different pixel on Website B, the pixel provider can match information (like the IP address) to build a unique profile for that visitor.

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