PETs in the wild: unpacking privacy-enhancing technologies

As digital advertising adapts to growing regulation and shifting user expectations, privacy-enhancing technologies (PETs) are increasingly coming to the fore. But while the term is cropping up with greater frequency, understanding of what PETs actually are - and how they can be applied in practice - remains patchy. At a breakfast briefing hosted at IAB UK, industry experts gathered to cut through the jargon, explore real-world use cases and discuss what’s needed to scale adoption. Here’s what we learnt... 

A response to rapid change 

Opening the session, Chloe Nicholls, Head of Ad Tech at IAB UK, set the scene by outlining the origins of PETs. “They’ve emerged due to the rapid development of our advertising ecosystem,” she said. “As the pace of innovation has grown, so have concerns about the lack of privacy. PETs aren’t just a privacy initiative - they can bring wider benefits across the supply chain.” 

Her remarks underlined the shifting narrative around PETs. Once seen solely as a privacy fix, these technologies are now being recognised for their potential to improve collaboration, enhance data processing and futureproof digital advertising. 

Balancing performance & privacy 

One contributor highlighted the central tension facing the industry: how do we continue to deliver impactful, personalised advertising while respecting people’s privacy? They outlined the polarising options: strip away all tracking entirely - or return to the "wild west" of the early 2010s. Neither extreme is viable - the challenge is to strike a meaningful balance. 

With opt-outs becoming more common, new data laws on the horizon and a patchwork of global regulations to navigate, the role of PETs is to enable continuity without compromise. Contributors stressed that while PETs are not new, they are more relevant than ever. Their success depends on industry-wide collaboration, from open-source code to consortium-led innovation. 

From theory to application 

Several speakers unpacked how PETs work in practice - starting with a memorable analogy known as "Yao’s Millionaire’s Problem". It describes how individuals can work out who earns the most in a group without revealing personal salaries. The idea helps illustrate how PETs enable privacy-preserving data analysis, allowing parties to generate insights without ever accessing raw personal data. 

Real-world examples included privacy-protected attribution models, where ad impressions are stored locally on a device and encrypted. If the user later converts, the advertiser can decrypt that record to track performance - but no one else can view or exploit the data trail. PETs such as federated learning and trusted execution environments (TEEs) offer similarly secure frameworks, keeping data decentralised and access tightly controlled. 

What makes a PET? 

The term “PETs” encompasses a broad range of technologies, but not everything privacy-related qualifies. It’s not enough to simply gather more consent - what matters is how the technology prevents the exposure of identifiable information. Input privacy refers to hiding the source of data; output privacy ensures individuals can’t be re-identified from results. Some PETs do both. 

A key theme was usability. PETs have existed in academic and tech environments for some time, but for mainstream adoption to grow, they need to be accessible and effective for everyday use. As one speaker put it: innovation tends to follow effective UX. Making PETs intuitive will be the key to embedding them more widely. 

The state of play & what's next 

Looking ahead, contributors agreed that a more integrated approach is taking shape. Rather than PETs being developed in isolation, many are now being driven by partnerships between brands, tech platforms and ad tech providers. Clean rooms, differential privacy settings and collaborative frameworks are helping accelerate adoption. 

The UK is viewed as a relatively advanced market in this space. Speakers pointed to the ICO’s progressive stance, centralised authority and clear guidance as important factors. However, there was also acknowledgement that progress is uneven globally - with some regions lagging behind due to legislative delays or fragmented regulation.