Every action on the web is tracked.

The data is captured through

• Cookies
• Tracking Pixels

A cookie is a small file that a website stores on your computer. It contains some information about your activity. The server will store their own files and match your cookie to the record on server. This allows to know if the user is returning, how much time between visits, and what ads they clicked.

Ad platform like Google and Facebook use cookies to identify users as they browse around the web. As you browse, the publishers will see list of websites you interacted with and serve you ads you are more likely to engage with. This is the base of Programmatic Advertising.

Alongside cookies, we have the tracking pixel. It stores information on the webserver, not on your computer. It is a 1x1 transparent image for tracking, often used to see if users convert after seeing a particular ad. The server stores a small file, pixel.gif, and every time it is asked for that file, it is going to log that requests: instead of asking just for pixel.gif, we add custom variables to the request, like pixel.gif?ID=123&ORDER=ABC.

The server will be successful in delivering the image, but it does keep a log of that unique URL, and can use the variables to match a transaction back to a particular user or advertising event.