If you’ve ever looked at a product online and then seen an ad for it everywhere, on social media, news sites or even YouTube you’ve likely experienced remarketing.
Cross tracking is the process of identifying and following a user as they browse around the web – this is often done using cookies, tracking pixels, or device identifiers. In the current modern digital world this is not a reliable form of tracking due to modern privacy regulations, consent, and browser based pixels being blocked by many browsers; this is no longer a reliable method for marketing tracking.
What is Cross-Site Tracking?
Cross-site tracking is the process of collecting data about a user’s activity across multiple websites.
It works by assigning identifiers (like cookies or device IDs) to users, allowing platforms to recognize them as they browse the internet.
This enables marketers to:
- Understand user behaviour
- Build audience profiles
- Deliver highly targeted ads
What is Retargeting (Remarketing)?
Retargeting’s main premise is to bring users back to the site who have already shown interest.
Example:
- You visit an online store and look at running shoes
- You leave without buying
- Later, you see ads for those same shoes on Instagram or a blog
That’s retargeting in action.
Retargeting itself can be done by both third and first party tracking. At TDS we would set this up to ensure that the user has consented to their data being used for marketing, ensuring consent is recorded before any data is stored. The user would then browse the site, interacting within your eco-systems; this then feeds into the available customer data we can use for retargeting which will be sorted and sent hashed from the server, to the ad platforms.
How Does it Actually Work?
This is how it used to work behind the scenes:
- A tracking pixel is installed
A small piece of code (often from ad platforms) is added to a website. - The user visits the site
When someone lands on the page, the pixel fires and collects data. - A cookie or ID is assigned
This allows the system to “recognize” the user later. - The user is added to an audience
For example: “People who viewed product X” - Ads are served across platforms
The user sees relevant ads on:
– Social media
– News sites
– Apps
– Search engines
Now with tighter privacy regulations, and a shift towards first party tracking, those who remain using browser based pixels will be left in the past; susceptible to data-loss and blocked pixels.
For some further context, these technologies could look like
- Cookies – small files stored in the browser to track user behaviour
- Tracking pixels – invisible scripts that send users data back to ad platforms
- Device fingerprinting – this identifies users based on device characteristics
- Customer Data Platforms (CDPs) – tools that unify data from multiple sources to build complete user profiles.
Why did marketers use this strategy?
The main benefit here was visibility, user data was easily accessible, and they were easy to implement. However, in 2026 this looks very different.
However, retargeting remains an extremely useful tool, which can still be used in a first party manner. Keeping consented user’s data within your digital eco-system
Privacy, Cookies, and the Future
This is where things are changing fast. Modern privacy regulations like General Data Protection Regulation (GDPR) and platform updates from companies like Apple and Google are reshaping how tracking works. Many browsers are now blocking pixels, cookies and third party tracking to protect their users’ privacy.
So… What’s Changing?
- Third-party cookies are being phased out
- Users must give consent for tracking
- Data transparency is now required
What’s replacing it:
- First-party data (collected directly from users)
- Server-side tracking
- Privacy-focused advertising models
Final Thoughts:
The strategy behind tracking users across the web, isn’t just about ads following you. Instead it’s part of a much larger picture that combines data collection, user behaviour analysis, personalization, and advertising.
Understanding that this can leave you with missing incomplete data, can help you understand your marketing performance. Good, clean data fuels ad platforms and is a crucial driver behind marketing efforts.
