Cookieless browsers win out in groundbreaking AOP, Anonymised trial


The Association of Online Publishers (AOP), in collaboration with Anonymised, today announced positive results from the initial testing phase of Anonymised’s privacy-enhancing technology.

AOP said the test — which commenced in November 2023 and was designed in conjunction with the UK Competition and Markets Authority — seeks to assess the effectiveness of Anonymised’s technology against third-party cookies and an “ID-less” scenario.

Cookieless browsers

The test is organised in two stages, with the first concluding in April 2024 and the second continuing through the summer.

The primary goal is to compare market outcomes for ads served using Anonymised’s technology with those served using third-party cookies.

“Advertisers supporting the testing framework include Curry’s, Arriva, E.ON, and several global entertainment brands.”

“This test marks a milestone in our efforts to future-proof publisher revenues in this period of transition for digital advertising,” said Richard Reeves, Managing Director of AOP.

“The initial findings underscore the potential of privacy-enhancing technologies like Anonymised to not only maintain, but enhance, ad performance and reach – even in a cookieless environment.

“These insights will be invaluable in guiding our members – and the industry as a whole – toward more privacy-conscious advertising solutions independent of big tech’s influence.”

Results and key findings

Key performance metrics evaluated include reach and frequency, performance, ease of use, and the customisability and optimisation of ad campaigns.

The initial phase of the test yielded promising results, demonstrating that Anonymised’s technology can outperform third-party cookies in several key areas:

  • Higher CPMs and performance: Campaigns using Anonymised on cookieless browsers showed higher CPMs and marginally better performance metrics. Anonymised sold an average of 68% of impressions on cookieless browsers, compared to 32% on cookie-based browsers.
  • Audience reach and impressions: The technology achieved approximately 83% audience addressability per publisher within 90 days of deployment. Anonymised successfully reached a significant proportion of cookieless users, with higher delivery rates on Safari and Firefox.
  • Click-Through Rates: CTRs for standard banner campaigns were slightly better on cookieless browsers (+5%) compared to cookie-based, while premium inventory CTRs were notably higher (+28%) on cookieless browsers.

The test also provided valuable technical and operational insights that will inform future efforts:

  • Technical findings: Anonymised’s technology demonstrated significant over-indexing on Safari and Firefox, with delivery rates between 3.5 and 5.5 times higher on cookieless browsers. This was attributed to differences in bidding logic and the prioritisation of non-user ID signals.
  • Operational findings: Though the use of Anonymised’s technology was found to be efficient and straightforward for buyers, default settings in DSPs still favour cookie-based configurations. Addressing this will require education and changes in platform UI and logic to fully leverage ID-less technologies.

“Working with Anonymised has been a great experience so far”, said Nino Stylianou, Head of Programmatic Yield at Mumsnet.

“The platform enables us to discover our audience’s actions when they aren’t with us; revealing behaviours we didn’t previously know were prevalent.

“It also enables quick and seamless activation and helps us to bring non-endemic campaigns that we may not have had access to in the past. We’re looking forward to doing more work with them!”

Mattia Fosci, CEO of Anonymised, said: “The results from the first phase of our test are very encouraging. We’ve demonstrated that it’s possible to deliver high-performing ad campaigns without relying on third-party cookies or other types of IDs”.

“This technology has arrived at a crucial juncture as the industry rushes to replace cookies with equivalent IDs that are likely to be short-lived.

“There needs to be a concerted effort to build independently operated advertising pipelines that keep data in the hands of publishers and users – as supported by the ICO – in order to avoid being held to ransom by big tech.”

Following the positive results from this first phase, the test now moves into its second phase, which will focus on scaling spend on targeting campaigns and automating optimisation; improving operational flows for self-serve campaigns; and testing and documenting retargeting, lookalike, and measurement functionalities.