Advertising plays a vital role in funding free-to-consume content on the open web. But while it’s essential to keeping digital content accessible, that doesn’t mean people will accept just any type of advertising. According to McKinsey, 71% of consumers expect companies to deliver personalised interactions, and that includes in their ads. To deliver highly personalised content to the right audience at the right moment, brands have long relied on cross-site tracking—also known as cross-website tracking. In this piece, we explore how cross-site tracking has worked in the past, and how it’s evolving in response to growing demands for privacy and transparency in the digital world.
What is cross-site tracking?
Cross-site tracking is a technique used by publishers and brands to monitor users’ browsing activity across multiple websites. Historically, cross-website tracking has been enabled by tracking cookies, which have helped brands to build detailed profiles of users’ interests, habits and behaviours. This data is then used to deliver targeted advertising and personalised experiences.
The problem with cross-website tracking
When conducted without informed user consent, cross-site tracking violates key global privacy regulations such as the GDPR (UK and EU), the California Consumer Privacy Act (CCPA), and the EU ePrivacy Directive, among others. While this is widely recognised by brands and publishers, compliance doesn’t end with consent. Sharing tracking data with third parties can still expose organisations to risk. The broader the data sharing, the higher the chances of misuse or breaches. Alarmingly, a recent WIRED analysis of the top 10,000 websites found that dozens share user data with over 1,000 companies, while thousands more share it with hundreds.
What’s next for cross-site tracking?
In a privacy-first era, cross-site tracking is undergoing a major transformation. Leading browsers now give users more control, allowing them to block third-party cookies and opt out of tracking entirely. With 70% of consumers already blocking cookies, the impact on traditional tracking methods is profound.
In response, brands and publishers are embracing privacy-preserving alternatives such as first-party data strategies and consent-based tracking solutions. With Google’s Privacy Sandbox facing repeated delays, attention is shifting to the growing ecosystem of alternative IDs. When implemented correctly, these solutions can help brands build trust, maintain personalisation, and honour user privacy through transparent, ethical data practices.
Telco-verified IDs: the evolution of cross-website tracking
Telco-verified IDs are a prime example of the new wave of privacy-first identifiers. These unique, brand- or publisher-specific IDs enable consistent user recognition, even when users aren’t logged in. By drawing on consented first-party cookies and linking them intelligently, this approach helps maintain customer experience and ad effectiveness in a privacy-conscious world.
Importantly, this is not cross-site tracking. Users are not followed as they browse the web. Instead, telco-verified IDs rely on network intelligence to verify pseudonymised visitors, without exchanging any personal data. This allows each publisher or brand to recognise their users across sites and devices, creating unified profiles while preserving anonymity. In effect, telco-verified IDs enable publishers and brands to know it is the same user accessing their sites and apps, without knowing who that user is.
Replacing cross-site tracking with cross-site verification
As the digital world becomes ever more privacy-centric, so too must the tools and strategies brands use to reach their audiences. Cross-site tracking, once the backbone of personalised advertising, is being re-evaluated in the light of growing privacy expectations and tighter regulations. Privacy-first solutions, such as telco-verified IDs, offer a way forward by respecting user consent while still enabling effective engagement.
These innovative technologies signal a more ethical and transparent future for digital advertising, one where identity can be verified without compromising personal data. Adapting to this new world is essential for brands and publishers as they look to maintain or grow revenues whilst complying with regulations to meet the needs and demands of consumers. Organisations that embrace privacy-first approaches will be best placed to deliver value to both users and advertisers in the next chapter of the open web.
