What is a tracking pixel? How modern tracking works so easily

Tracking pixels have played a key role in online marketing for years, as they provide reliable data on user behaviour, allowing per­son­al­ised ad­vert­ising and sales campaigns. In­teg­rat­ing tracking pixels into websites and emails is not par­tic­u­larly com­plic­ated. However, con­cern­ing data pro­tec­tion, companies should def­in­itely comply with GDPR when using tracking tech­niques.

What is a tracking pixel?

A tracking pixel is defined in online marketing as a graphic element embedded in the code of websites, online ad­vert­ise­ments, or emails. It is usually just one pixel wide and one pixel high, thus also called a 1x1 pixel or single-pixel image. Due to its small size, the tracking pixel does not affect the load times of emails, ad­vert­ise­ments, and websites. Other common terms for the tracking pixel include the following:

• Counting pixel
• Pixel tag
• On-site or website pixel
• Pixel method
• Clear GIF
• Web bug
• Web spy
• Web beacon

Oc­ca­sion­ally, it is also referred to as an IVW pixel. This term indicates that the tracking pixel for measuring reach is loaded from a resource of the Inform­a­tion Society for the Veri­fic­a­tion of the Dis­sem­in­a­tion of Advert­ising Media e.V.

Tracking pixels are usually col­our­less and trans­par­ent (hence the term ‘Clear GIF’) and perform their tasks unnoticed behind the scenes. Within in­ter­con­nec­ted backend processes beyond user ex­per­i­ence, they are used in online marketing and e-commerce for the col­lec­tion and analysis of user data. Through tracking pixels, companies gather in­form­a­tion about the reach of online and email marketing, allowing them to optimise their sales and marketing strategies.

What data do tracking pixels collect?

Strictly speaking, pixel tags are used to count website visits. However, when a tracking pixel is accessed, ad­di­tion­al data is also collected and stored in server log files for the purpose of logfile analysis. The pixel request can also trigger the setting of cookies, which also play an important role in tracking. Combined with cookies and other tracking methods, tracking pixels today are involved in col­lect­ing a wealth of in­form­a­tion:

• Browser type and version
• Operating system used
• Device type (e.g., mobile device or desktop computer)
• Client used (e.g., browser or email ap­plic­a­tion)
• Screen res­ol­u­tion
• Referrer URL (the address of the previous website visited)
• IP address (used to infer the internet service provider and ap­prox­im­ate location — essential for geotar­get­ing)
• Data on the customer journey (e.g., user movement across the site, search behaviour, clicked links or ads — often tracked via multiple pixels)
• Date and time of a server request (triggered by opening an email or webpage)
• Opening, opening time, and for­ward­ing of emails
• Click-through rate (link tracking)
• Time and date of a page view (including a de­scrip­tion of the page where the tracking pixel is located. This allows, for example, trans­ac­tions in affiliate marketing to be tracked)

Since this and other data can be collected across servers and pages, modern tracking provides a com­pre­hens­ive picture of the browsing, shopping, and con­sump­tion behaviour of website visitors.

How tracking pixels work and where they’re embedded

Embedding tracking pixels with HTML and CSS

To enable tracking pixels to perform their tasks, you need to modify the source code of a webpage or an email and embed a tracking pixel. A simple HTML code snippet ensures that the tracking pixel is loaded from a specific address (tracking pixel URL) when the page is accessed and is provided with a char­ac­ter­ist­ic display size (1x1 pixel). You can also set the values for width and height to ‘0’ to com­pletely suppress the display of the tracking pixel:

< img src="Tracking pixel URL" width="1" height="1">

The ap­pear­ance of modern websites is usually more precisely defined with special style templates called Cascading Style Sheets (CSS). The style attribute visibility:hidden specifies that a tracking pixel should be hidden. The CSS attribute position:absolute ensures that the pixel tag is com­pletely removed from the normal flow of the page layout:

< img src="Tracking pixel URL" style="position:absolute; visibility:hidden">

To com­pletely suppress a display, you can use display:none:

< img src="Tracking pixel URL" style="display:none">

The code blocks can be manually inserted into a website’s source code during page tagging. If you use a content man­age­ment system, tracking pixels can also be con­veni­ently con­figured and in­teg­rated with a plugin. For WordPress, you can use the Pixel Tag Manager PixelY­ourSite for this purpose, for example.

Tracking pixel in JavaS­cript

Modern tracking often uses more complex code. By using JavaS­cript, you can trigger the tracking pixel script-based and learn even more about users as well as the software and hardware they use. The classic HTML in­teg­ra­tion of website pixels is usually part of a dual strategy: With so-called JavaS­cript tags, you first try to achieve the best in tracking and data col­lec­tion.

If this method doesn’t work, the simple HTML code for trig­ger­ing tracking pixels is used as an al­tern­at­ive and ensures that important tracking data is trans­ferred. The tracking pixel is embedded in a special tag (<noscript>) that the reading browser processes if JavaS­cript is disabled. Facebook uses such a ‘Plan B code’ for in­teg­rat­ing the Facebook pixel:

<noscript>
<img height="1" width="1" style="display:none"
src="https://www.facebook.com/tr?id={insert Pixel ID here}&ev=PageView&noscript=1"/>
</noscript>

In affiliate marketing, tracking pixels can be cus­tom­ised with ad­di­tion­al para­met­ers to enable precise at­tri­bu­tion. For example, shop IDs, order IDs, and revenue values are often appended to the pixel URL. This allows affiliate networks to track in­di­vidu­al trans­ac­tions for com­mis­sion and reporting purposes. Here’s a typical example of such a tracking pixel in use:

<img 
src="https://www.example-affiliate.com/track?shop_id=SHOP-ID&order_id=ORDERID&revenue=TOTAL-VALUE" 
width="1" height="1"
/>

A tracking pixel is triggered when, for example, an online shop page is accessed via a mouse click and loaded in the browser (e.g., Google Chrome). The browser reads the code snippet for the tracking pixel and requests the tiny image using the stored tracking pixel URL. The addressed server then sends the pixel tag to the client’s browser, counts the page view, and logs the unique IP address of the recipient as well as other visitor in­form­a­tion sent during the request procedure in log files. These records are then used for quant­it­at­ive (stat­ist­ic­al) and qual­it­at­ive analysis in online marketing.

Which web analytics tools work with tracking pixels?

Web analytics tools are used for eval­u­ation. Some of the most well-known tools and services of this type include Google Analytics, etracker, and the open-source web analytics platform Matomo (formerly Piwik). Facebook customers integrate tracking data with the Meta Pixel analysis tool using the ap­pro­pri­ate embedding code. In email marketing, tracking pixel data can be evaluated with tools such as the following:

• MailChimp
• Brevo
• Clev­er­Reach
• GetRe­sponse
• Campaign Monitor

Nowadays, it’s common to use a special technical in­fra­struc­ture for col­lect­ing and recording user data. Often, a specific third-party server (tracking server) is used to redirect links, capturing all relevant tracking data for reporting. In many cases, a dedicated database stores and maintains this massive data col­lec­tion.

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Ad­vant­ages and dis­ad­vant­ages of tracking pixels

Ad­vant­ages of tracking pixels

Tracking pixels offer numerous ad­vant­ages to users:

✓ Data on user behaviour: Website pixels provide data about user behaviour, traffic, and page per­form­ance, and can con­trib­ute to op­tim­ising online strategies and ad­vert­ising campaigns.

✓ Social media activ­it­ies and search engine op­tim­isa­tion (SEO): Together with web analytics tools like Google Analytics, tracking pixels provide a broad data found­a­tion and offer valuable insights into marketing per­form­ance and customer behaviour. The solid data found­a­tion of pixel-based tracking benefits campaign op­tim­isa­tion, content strategy, and user targeting across platforms.

✓ Targeting: The data found­a­tion minimises waste in targeting audiences, allowing the placement of ad­vert­ising elements on websites or search engines to be more precise.

✓ Support for sales and E-commerce strategies: Tracking pixels enable the tracking of the customer journey. When on-site pixels are placed on all pages of an online store, the activ­it­ies of in­di­vidu­al customers can be captured com­pre­hens­ively. So-called con­ver­sion pixels are placed on stra­tegic­ally important pages that customers can only access after re­gis­ter­ing or making a purchase (e.g., on the thank-you page after purchase). These website pixels allow for reliable meas­ure­ment of whether and how often customer interest actually led to a product purchase (sales con­ver­sion).

✓ Improved con­ver­sion rate op­tim­isa­tion: Con­tinu­ous and ongoing customer tracking allows for precise iden­ti­fic­a­tion of drop-off points in the customer journey and weak­nesses in the user ex­per­i­ence design and usability of a web offering.

✓ Marketing: Pixel-based tracking can gather in­form­a­tion that is helpful for choosing ad­vert­ising media and selecting suitable ad­vert­ising contexts. Moreover, it can improve customer ac­quis­i­tion and support lead gen­er­a­tion (leads refer to the ini­ti­ation of contacts).

✓ Un­der­stand­ing Customer Per­spect­ive: By analysing tracking pixel data, the customer journey can be visu­al­ised in the form of a customer journey map and in­ter­ac­tions between customer and brand can be il­lus­trated. This is in­sight­ful for companies as they can analyse and assess their sales and marketing activ­it­ies from their customers’ per­spect­ive.

✓ Simple im­ple­ment­a­tion: The im­ple­ment­a­tion of basic tracking pixels is straight­for­ward.

✓ Func­tion­al­ity: Tracking pixels embedded in web pages, emails, or ads work reliably — even when JavaS­cript is disabled. Thanks to their minimal size, pixel tags have virtually no effect on a website’s loading times.

Dis­ad­vant­ages of tracking pixels

However, the use of tracking tech­niques should not be overdone, as they can also have negative effects.

✗ Increased loading times: Using numerous marketing pixels for various purposes can indeed slow down page loading. The browser then com­mu­nic­ates with different software in­ter­faces and servers, which should be easily reachable and not over­loaded at that moment. Per­form­ance can also suffer if you use tracking tools from multiple providers sim­ul­tan­eously (e.g., Google Analytics, WP Stat­ist­ics, Facebook Pixel).

✗ Im­ple­ment­a­tion issues: Delays often result from faulty im­ple­ment­a­tion of tracking pixels and JavaS­cript tags in the source code. If a special plugin is used for tracking in the CMS, it should be proven and per­form­ance-optimised; otherwise, it may take too long to load and trigger the pixel tags.

✗ Blocked pixels: The trig­ger­ing of tracking pixels can be prevented by blocking images. This option is often used on mobile devices to reduce data traffic from volume-based plans and thus save costs.

✗ Security risks: Tracking pixels are often misused and employed in spam emails to verify email addresses. When a user opens a spam email, the tracking pixel is loaded and the address is re­cog­nised as valid and re­gistered in the hacker network. This is followed by countless other unwanted spam and phishing emails to the account verified in this way. Ad­di­tion­ally, the use of pixel-based tracking tech­no­logy can lead to targeted ma­nip­u­la­tions, such as visitor exchange systems or click software.

Tracking pixel and data privacy

Since they document and track user behaviour, tracking tech­niques have long faced criticism from privacy advocates. This criticism has in­tens­i­fied with the GDPR, which has been enforced through­out the EU since 2018, defining a very high standard of data privacy by in­ter­na­tion­al com­par­is­on. Privacy advocates par­tic­u­larly criticise that tracking pixels operate unnoticed in the back­ground and do not reveal them­selves to users. Ad­di­tion­ally, the extent of the collected data and its further pro­cessing are not trans­par­ent to users.

Tracking is viewed as par­tic­u­larly con­cern­ing when it:

• Collects data without anonymity and without the user’s knowledge or explicit consent, leading to a direct personal reference. This happens, for example, when email news­let­ters include tracking pixels that can be linked to a user’s private email address or a uniquely assigned tracking ID.

• Is used for extensive user profiling, often by combining tracking tech­niques such as cookies with data from various sources — for instance, merging browsing behaviour with social media activity.

• Shares data with third parties. Privacy advocates view the sale or transfer of personal data for further analysis or marketing as a legal grey area — es­pe­cially when U.S.-based companies like Google Analytics are involved. In the United States, law en­force­ment, in­tel­li­gence agencies, and gov­ern­ment bodies can access user data at any time.

To avoid sanctions and fines, companies should always act in full com­pli­ance with the GDPR and process data in an encrypted and non-iden­ti­fi­able form — that is, an­onymised or pseud­onymised. If tracking methods involving personal data are still used, busi­nesses and online store operators should obtain explicit user consent through a GDPR-compliant consent tool. This process is commonly referred to as an opt-in procedure.

In addition, it is essential to include a section on tracking pixels in your website’s privacy policy. Any transfer of data to the United States or other non-EU countries should be carefully evaluated in light of GDPR re­quire­ments and the un­ex­pec­ted end of the Privacy Shield agreement.

Since the legal landscape is both complex and evolving — and because GDPR com­pli­ance is being reviewed more fre­quently for websites and online shops — busi­nesses should not take un­ne­ces­sary risks. When in doubt, it’s best to consult a qualified data pro­tec­tion expert.

Pro­tec­tion from tracking

If users want to actively protect them­selves from tracking, they can install ap­pro­pri­ate browser plugins—such as those for blocking JavaS­cript—and adjust browser security settings to com­pletely block or only tem­por­ar­ily allow cookies. By generally disabling images in email programs and browsers, users can ef­fect­ively defend against tracking pixels, though this may result in limited email and webpage display.

You can act more flexibly by making the loading and display of images con­tin­gent on your consent. However, each case must then be in­di­vidu­ally examined. In email programs, it’s possible to disable support for emails in HTML format, thereby pre­vent­ing the download of tracking pixels. Using proxy servers or the Tor browser can also help avoid tracking pixels and prevent entries in server log files.

Please note the legal notice for this article.