A tracking pixel (also called 1x1 pixel or pixel tag) is a graphic with dimensions of 1x1 pixels that is loaded when a user visits a website or opens an email, and is used to track certain user activities. With a tracking pixel, advertisers can acquire data for online marketing, web analysis or email marketing. With log file analysis, long data evaluation or using appropriate analytical tools, this data can be used for different purposes, for example retargeting.
A tracking pixel is a graphic that mostly has dimensions of only 1x1 pixels. Because it is so small, it can hardly be seen by visitors of a website or email recipients. These tracking pixels are partly or fully designed to be transparent, or camouflaged in the background color of the website so that they don't stand out to users. Users are usually not supposed to see the tracking pixel. The focus is mainly on the processes that are initiated by downloading the tracking pixel.
Tracking pixels within the source code might look like this:
<img src=“Tracking Pixel URL” style=“position:absolute; visibility:hidden”>
<img src=“Tracking Pixel URL” style=“display:none”>
<img src=“Tracking Pixel URL” width=“0” height=“0”>
The tracking pixel URL is the memory location on the server. When the user visits a website, the image with the <img> tag is loaded from this server. Optical properties such as visibility, or a very small size are defined using the style attribute.
The website operator or sender of an email adds the tracking pixel using a code in the website’s HTML code or email. This code contains an external link to the pixel server. If a user visits the destination website, the HTML code is processed by the client – usually the user’s browser. The browser follows the link and opens the (invisible) graphic. This call is registered and noted in the server’s log files.
The following data can be acquired and analyzed with a tracking pixel.
Tracking pixels are often criticized by data protection advocates because they collect comprehensive data about the user, mostly without knowledge of the user. As the tracking pixel cannot be seen with the naked eye, and the common user doesn't recognise the meaning of the small graphic even when it is visible, the tracking pixel involves a transfer of information without consent. Based on this, critics argue that with tracking pixels, user privacy is violated through the recording of a motion profile. The transmission of the IP address also makes it possible to match information to other information on the Internet, e.g., to a profile in a social network or forum.
Tracking pixels also simplify the work of spammers. Spammers can integrate tracking pixels in their spam mails in order to find out if an email address is valid. If the recipient opens the email and thereby loads the automated tracking pixel, the spammer receives a confirmation of the authenticity of the email address. As a result, the sending of spam messages increases.
The use of tracking pixels is beneficial for website operators, SEOs and email senders. This is because they can use the generated information to improve their online offers, make them more user-friendly, and adapt the offers to the most commonly used browser types and versions.
Tracking pixels can also be beneficial in the analysis of sent email newsletters. This is because they show the opening rates of certain emails or newsletters through the user statistics data. Together with A/B tests, successful campaigns can thus be filtered out. From the recipient’s point of view, this has the advantage that newsletters in the future can be designed to be more relevant and interesting.
Possible measures to restrict the functioning of tracking pixels:
Tracking pixels generally have similar functionalities as cookies. The tracks of the user are recorded by a file that is saved in the user’s hard drive. However, more and more users are nowadays taking up measures to block cookies using the browser functions. As a result, cookies often end up providing incomplete data and their use is at times blocked completely.
The tracking pixel is therefore used as an alternative to the cookie since its use cannot currently be blocked by a normal browser. Even so, several browser extensions, plugins, and programs that enable blocking of tracking pixels and hence prevent a log file analysis already exist. Tracking methods such as Canvas Fingerprinting, Event Tracking, or different hybrid methods are also being used increasingly and as with all tracking models, comprehensive changes in the websites are necessary – e.g., in data protection. In addition, user consent to allow the tracking with pixels must be obtained.