The Topics API is Google’s latest replacement for the third-party cookie and aims to create a privacy-focused, interest-based advertising model. But what is Topics? How does it work? And why was it created? Here, we answer these questions and many more

As one of the world’s biggest players in digital advertising, all eyes are on Google and what its plans are for a successor to the third-party cookie. The outcome will play a huge part in reshaping a multi-billion-dollar industry with an uncertain future.

While Google’s initial alternative was the Federated Learning of Cohorts (FLoC), the tech giant has since ceased its development in favor of an advertising system called Topics.

In this article, we examine what the Topics API is, how it works, and why it was created. We’ll also take a closer look at FLoC, exploring the criticism it received and the reasons why it was abandoned.

What is Google Topics?

Topics is Google’s proposed privacy-friendly replacement for third-party cookies. It’s a browser-based system that assigns a user a set of interests according to the websites they have visited.

Once these interests have been allocated, the Topics API shares them with participating websites and ad tech companies to power personalized digital advertising.

With all tracking happening on-device, data only being stored for a maximum of three weeks, and no information shared with any external servers (including its own), Google is presenting the Topics API as a potential compromise between ad personalization and user privacy that will shape the future of the post-cookie industry. The company is, however, careful to note in its explainer that the technology is still in the early stages of testing.

How does Google Topics work?

If your browser supports Topics, each week it will automatically assign you a number of categories (or ‘topics’) based on the websites you’ve visited.

Examples of these categories could be Travel & Transportation or Books & Literature. They will be selected from an initial list of 350 that has been curated by Google, a number that is likely to increase as the product evolves, and will not include anything sensitive such as gender or race.

Once Topics has created three of these weekly batches, it will randomly select one category from each batch to share with a participating website that you visit.

The participating website (or the ad tech company that manages its inventory) then uses this information to serve you targeted digital ads while you’re there.

Google has stated that Topics will only ever hold data from a maximum three-week period. So, when week four begins, all categories from week one are deleted, and when week five begins all categories from week two are deleted, and so on.

The aim is to create a form of targeting that keeps the user’s personal data completely anonymous, which Google describes as interest-based advertising.

Can you opt out of Google Topics?

Yes, websites and users can both opt out of Google’s Topics API.

This is because Topics requires the participation of four parties to work: the browser, the user, the website being visited, and the website serving the advertising.

With Topics st