Tracking Pixels

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Tracking pixels can be classified as a technique used on web pages or in emails to collect information about the behavior of users. Tracking pixels are 1x1 pixel large, usually transparent graphics that are built into the respective website. Other common terms for tracking pixels are pixel tag, web beacon, web bug or clear GIF. Pixel tags implemented with JavaScript are often referred to as JavaScript tags.

How do tracking pixels work?

Tracking pixels
Figure: Tracking Pixels - Author: Seobility - License: CC BY-SA 4.0

The very small size of a tracking pixel is an essential part of its functionality. Tracking pixels are intentionally hidden in the background of a web page or email so that they are not part of the user experience. The intention behind this is to enable a back-end process that does not distract from the content of a website or marketing email.

Tracking pixels are embedded in the HTML code of a website, online ad, or marketing email and are retrieved from the server every time a user loads that website, ad, or email into their web browser. The server then sends the pixel tag to the user's unique IP address and logs it. The server thus counts the number of retrievals.

What are tracking pixels used for?

Tracking unique page-views is the most basic function of a tracking pixel. Web site operators, email marketers or advertisers who use a tracking pixel can analyze the server logs and see how many unique page-views their content has received.

The traffic data collected with a tracking pixel can then be further analyzed, e.g. for marketing purposes. More accurate analysis of IP addresses can provide a basic idea of where users come from geographically and what type of devices and operating systems they use to visit a website. Tracking pixels also work across websites and servers, giving website owners and advertisers a clearer view of what users are looking for and why they are visiting the site. This data can be used to tailor content and ads to users' needs through targeted marketing campaigns.

Integration of a tracking pixel into HTML code

Tracking pixels can be integrated into the source code of a website as follows:

<img src="URL tracking pixel" width="0" height="0">
<img src="URL tracking pixel" style="position:absolute; visibility:hidden">
<img src="URL tracking pixel" style="display:none">

When a visitor accesses a site, the tracking pixel is loaded from the server using the <img> tag. "URL tracking pixel" indicates the location of the image on the server. The style attributes "visibility:hidden" and "display:none" specify that the image is hidden or not displayed. Alternatively, as in the first example, the values for width and height of the image can be set to "0" to prevent the tracking pixel from being displayed.

What is the difference between tracking pixels and cookies?

Unlike tracking pixels, cookies contain code that web servers use to store certain information in a user's browser. This information can then be retrieved at a later time for various purposes.

Ad servers, such as DoubleClick, use cookies to set unique user IDs that allow them to identify the same user across multiple touchpoints. When an ad server receives an ad request from a user who does not yet have such a cookie, the ad server assigns it a new unique ID. This ID is a random alphanumeric string. For each subsequent request, the cookie returns the same unique ID so that the ad server can recognize that it is the same user. Since all requests are recorded by the ad server, reports can be generated that provide a record of all touch points for each user. This functionality is not available for counting pixels.

Advantages and criticism of the use of tracking pixels

The advantage of tracking pixels for advertisers and website owners lies in the simple implementation of tracking pixels in websites, emails, and advertisements.

However, tracking pixels are often criticized with regard to data security aspects. Although collecting data about user behavior can be extremely helpful for marketing campaigns, the information is usually collected and transmitted without the knowledge or consent of users. In this respect, the privacy of users is violated by recording their behavior. In addition, it is easy to use the IP address to combine the collected information with other information and user profiles from social media, for example.

How can users protect themselves from tracking pixels?

Most modern browsers include a setting that can be used to prevent tracking. With special programs and plugins such as adblockers, users can also make tracking pixels visible or block them. Proxy servers or the Tor Browser also prevent the download of tracking pixels and an entry in the log files of the servers. Users can adjust their browser settings so that images are only loaded and displayed with their permission. Additionally, it is possible to turn off support for HTML mails in e-mail programs, so that they are not displayed, thus preventing the download of a tracking pixel.

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