Google Ads

Results from Google Ads’ interest-based advertising testing

Visual depiction of different affinities and an interest-based ad with privacy at its core

As Chrome’s deprecation of third-party cookies approaches, Google Ads and Display & Video 360 have been experimenting with interest-based audience solutions. This includes affinity, in-market, custom audiences and demographic segments on Google’s display network, using a combination of privacy-preserving signals.

In the first quarter of 2023, Google’s ads platforms conducted an experiment to understand how our interest-based audience (IBA) solutions perform when they rely on a combination of privacy-preserving signals. These signals included contextual information, the Topics API from the Privacy Sandbox and first-party identifiers such as Publisher Provided IDs. Our research did not compare the performance of third-party cookies to the Topics API alone, but rather a broader suite of signals available in a privacy-first world.

We created two experiment arms on a share of Chrome traffic. On one arm, we continued using third-party cookies. On the other, we replaced third-party cookies with a combination of privacy preserving signals for IBA solutions while maintaining the use of third-party cookies for other use cases such as measurement and remarketing.

Experiment setup for interest-based advertising comparing third-party cookies with a combination of privacy-preserving signals

What we learned

We learned that interest-based audience solutions with privacy-preserving signals showed promise compared to third party cookies. The experiment showed that when using interest-based audience (IBA) solutions with privacy-preserving signals on the display network, Google Display Ads advertiser spending on IBA — as a proxy for scale reached — decreased by 2-7% compared to third-party-cookie-based results. For conversions per dollar, as a proxy for return on investment, the decrease was 1-3%.1 Finally, we also observed that click-through rates remained within 90% of the status quo.2 And we observed similar performance for Display & Video 360.

The experiment also suggests that AI-powered optimization solutions can positively impact campaign performance. For example, campaigns using optimized targeting or Maximize conversions bid strategies were less impacted by the removal of third-party cookies, indicating that machine learning can play a significant role in driving results.

These results — while encouraging — should not be considered as an unequivocal indicator of Google’s IBA performance after the third-party cookie deprecation. The current experiment measures the effectiveness of serving interest-based audiences; the results of future experiments including measurement, remarketing, and other use cases may vary.

Why this work matters

Our industry is at a crossroads where the future of digital advertising and the open internet as we know it is at stake. Some are turning to blocking personalized advertising outright — which can lead to more intrusive forms of tracking such as fingerprinting — while others are building alternative identifiers to track people across the web and apps. We believe that neither of these are good outcomes for user privacy and that ad tech platforms can set a new standard for privacy, meet consumers’ expectations, and give businesses the tools they need to grow through the power of innovation.

Over the coming months, we’ll continue to iterate and run more rounds of testing in consultation with the Competition and Markets Authority in the UK. We’ll continue to provide regular feedback to Chrome and publish our findings to the broader industry to help improve Topics as it continues to evolve. We’re also making progress on our remarketing and conversion measurement experiments, so stay tuned as we’ll share our findings later this year.

Meanwhile, as an advertiser, make sure you continue adopting innovative ads solutions that protect people’s privacy and help you drive performance.

More Information


Google Internal Data, Global, Feb - Mar 2023


Google Internal Data, Global, Feb - Mar 2023