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In January 2022, Google announced that it would replace FLoC with Google Topics API, a Privacy Sandbox proposal to promote interest-based advertising.

Now, if you are new to these terminologies, let me simplify that for you.

Google plans on deprecating third-party cookies on Chrome from 2023 or 2024. For this purpose, they developed a “Privacy Sandbox” with proposed tools and APIs. This initiative was taken to enhance online privacy for users.

In addition, it aimed at providing developers, creators, and developers with tools to create thriving businesses while ensuring safety and security online.

However, the plan was actually made for 2022 but got delayed, maybe because they were working on a new solution after the negative feedback received for FLoC.

In this article, I’ll discuss what Google Topics API and FLoC are and help you understand how the Topics API can help you.

Stay tuned!

What Is FLoC?

Federated Learning of Cohorts (FLoC) is Google’s initially proposed solution for interest-based advertising with no third-party cookies.

Now, interest-based advertising (IBA) is a form of advertising where a user is served advertisements based on their specific interest inferred by the websites they visit.

It’s a powerful technique to help advertisers and businesses reach the right customers while the users can see the ads they are interested in. But in order to enable this, users’ information is gathered with the help of third-party cookies, which is not privacy-focussed.

So, FLoC would enable ads without sharing users’ browsing behavior. It leverages the FLoC algorithm to create its interest cohort or group for browsers with similar browsing histories. Next, it would report the anonymous cohorts to sites for ads.

However, FLoC had some flaws, such as a lack of transparency and clarity for users, along with security risks. And to counter those, they created another, better solution – Google Topics API. So, let’s finally talk about it. 

Also read: Federated Learning: A Paradigm Shift in AI and Machine Learning

What Is Google Topic API?

Google Topics API is a newly proposed Privacy Sandbox for interest-based advertising, replacing the earlier FLoC proposal.

With the Topic API, your web browser can determine the number of topics, such as music, food, sports, travel, tech, etc., representing your top interests in a week based on your browsing history. These topics will be kept only for three weeks, and then the old topics will be deleted.

Topics are chosen completely on users’ devices and not on external servers. So, when you visit a website where Google Topics API is enabled, it will choose only three topics, each from the last three weeks, and share them with the website and its advertisers.

This way, Topics enables web browsers to offer better control and transparency to users over their information. You will also have user controls in Chrome to view the topics and delete the ones you don’t like.

Furthermore, topics are curated thoughtfully, excluding sensitive categories such as race, gender, etc. Since Google Topics is enabled in Chrome, you can better view your data and control how it’s shared. Also, businesses don’t have to involve tracking methods, such as browser fingerprinting, to serve relevant advertisements.

FLoC vs. Google Topic API

The FLoC API generates an alphanumeric ID reflecting a user’s browsing patterns on Chrome. In addition, it’s unable to address issues concerning browser fingerprinting, sensitivity, etc. Overall, FLoC is not very good at protecting user privacy.

Therefore, Google came up with another idea after rigorous testing and working on the feedback. It’s all set to replace FLoC with Google Topics API. This is expected to benefit both the end users and advertisers with interest-based advertising with a focus on privacy.

Here are some points of improvements Topics brings over FLoC:

Reduced Fingerprinting

As discussed above, FLoC was criticized for not providing safety against browser fingerprinting with the use of a user’s FLoC ID. But no one likes to be tracked or expose their personal information.

To this, Google Topics API takes a different approach by distributing each topic to many users with certain interests while preserving privacy. Also, Topics can learn only one topic a week from regular users instead of gathering an insane amount of data and recommending something out of it.

Better Control

Once Google Topics is enabled, it will be highlighted in Chrome’s browser settings. So you will have better control over the topics. You can remove the ones you don’t like and get targeted only for the topics you are interested in. Plus, the topics will be erased after clearing the browsing history and won’t be available when you browse in incognito mode.

It’s beneficial for both a website owner and the user. As a user, if you opt out of the Topics, you won’t have your topics stored depending on your browsing history.

Similarly, if a site opts out from Topics, your web page won’t be considered in the topic distribution or definition process for your users. All this improves not only control and data privacy but also transparency.

Excludes Sensitive Categories

FLoC relies on machine learning to group users with similar interests into cohorts as per their browsing behavior. This could lead to grouping users based on certain sensitive categories like race.

But Google Topics does not target users based on categories that are sensitive, such as race, religion, sexual orientation, ethnicity, etc., unlike FLoC.

Instead, Topics lists different categories that are fully public and human-curated, excluding sensitive topics. In addition, users, as well as website owners, can opt-out of Google Topics API and choose not to participate in the API’s logic.


There wasn’t a defined reason for how users are grouped in FLoC; hence, the term “federated” is used in it. So, if you want FLoC IDs to make actionable for your marketing efforts, you would need to perform some additional data science and intelligence processes.

On the other hand, Google Topics provides an out-of-the-box solution for interest-based grouping and targeting, which is easier to comprehend. This way, website owners can easily collect insights about the high-level interests of users and audiences using Google Topics API and target accordingly.

Despite all the above benefits of Google Topics API over FLoC, marketers and privacy advocates still have certain concerns about it. The reason is, Topics still exposes user interests for ads, if not the user. They still weigh purely contextual solutions for ads over Google Topics.

Plus, it provides less granularity than FLoC. But marketers and site owners are keen to learn the Topics’ effectiveness to improve targeting without revealing user information.

How Does Google Topic API Work?

At the time of writing this article, Google Topics API is at the beginning of the discussion phase to collect and execute the feedback. Its design is not yet final. Based on the information available presently, here’s how Topics works.

To enable interest-based advertising, Google Topics API ensures the topics or categories are up to date to serve relevant ads. With this solution, your browser would suggest topics based on your browsing activity during a given period called “epoch”, which is one week according to the current proposal.

So, for each epoch, the Topics will randomly choose a topic based on your top five interests for this period.

There are about 350 categories to choose from, and the list is expanding. You can check its GitHub page to know more about all the topics and sub-topics. Some of them are science, finance, travel, sports, business, news, the internet, food and drink, art and entertainment, shopping, and more.

And to ensure all topics are presented and safeguard privacy, there’s a 5% chance of choosing a topic randomly from all the possible topics highlighted in the Taxonomy.

Google Topics API aims at enabling interest-based ads without sharing data with more people than what’s currently being done using third-party cookies. It also proposes that it will return topics for API callers who already have observed the topics within a given timeframe.

What Is Topic API Caller?

A Topics API caller refers to an entity invoking the JavaScript method – document.browsingTopics() and uses the returned topic of the method to choose relevant ads.

In general, calling this method is done using third-party code added to the website. The web browser will determine the API caller from the current document website.

Thus, if you are a third-party visiting a web page, ensure to call the Topics API from your site. Simply put, if you want the above method to return a topic or more topics, call the method from the same place where the topics were observed.  

Overall, you must understand these three things to know how Google Topics API exactly works.

  • How it assigns topics to users
  • How it assigns topics to sites
  • How it assigns topics to advertisers

Let’s expand them further.

How Does Topics API Assign Topics to Users?

Before a solution like Google Topics API, advertisers collected different types of data from users, such as deep behavioral information, intent, and third-party data. But Topics is changing this.

Currently, there is a limited number of topics available, but it’s expected to increase without any sensitive identifiers like race or religion.

Google Chrome will collect the top five categories for each user weekly by analyzing the number of visits of a user to a web domain from their browsing history.

It counts each page view as an individual visit but uses only the domain name to increase the visits assigned to a given topic. In addition, it won’t utilize your browsing history in the cloud; hence, your topics could vary across your different devices.

You won’t find it hard to comprehend the API and can easily view what data is collected, when it’s used, and enable/disable the solution. Unlike FLoC’s ambiguity, Topics provides human-readable topics.

How Does Topics API Assign Topics to Websites?

Google Topics API labels each site with high-level categories. To enable better contextual advertising, it will choose topics based on a user’s most frequent browsing behavior and visits. Next, it will share this data (and not that of the user) with advertisers and website owners.

Here, the interest-based topics are less granular, indicating a user’s current interests. For example, it will group a site about poetry, novels, language learning, and children’s literature will all be grouped as “Books & Literature”.

A handful of categories served will typically last for around three weeks. Hence, advertisers and site owners can target the audience with ads based on these categories that align with the users’ top interests.

For example, if the assigned targets have interests like beauty, health, and entertainment, they will see ads around these topics, not automobiles.

But if a user is assigned with interests like automobiles as one of the top topics in a week, advertisers and site owners would be capable of delivering advertisements based on these targets.

Initially, humans can map the sites to topics and let Google use the data created by humans to create an ML model and automate the overall process. Google will then map sites (hostnames and not each URL) to topics listed in a standardized taxonomy containing categories and subcategories.

How Does Topics API Assign Topics to Advertisers?

For advertisers, Google Topics API does three things to assign topics to them:

  • Identifies the top interests of a site’s visitors
  • Maps site hostnames to its user’s topics of interest
  • Assigns topics of interest to advertisers or ad platforms

First, it will use an ML model with classifiers distributed with the web browser to gather the topics based on the web pages visited by a user on a hostname.

Next, the classifier will store a user’s top five topics of interest. And to maintain privacy, Google says not to store those topics; instead, keep them only in the browser.

So, when someone visits a site and an ad call is made, Google Topics API will return the topics of interest to the advertiser. It will randomly fetch three topics from the stored list and a new topic from the full list.

Here, the advertisers must keep in mind that this process won’t bring any outside information. The topic assigned will be purely based on observation from previous site visits.

Furthermore, programmatic advertisers can also access Topics API while the ad call is still on. It’s possible through ad vendors to make advertising even easier and more effective so you can target the audience from multiple channels.

And if you want to enable the Topic API, embed its code on your site and participate.

But what if you don’t want it?

Let’s figure out if that’s possible and how.

Can You Opt Out of Topics API?

If you want to avoid Topics, it’s possible. Yes, you can opt-out of Google Topics API in Chrome via its Privacy Sandbox settings.

The reason why you can opt out is that Topics requires four parties to participate in order for it to work. These are – the user, the web browser, the site the user is visiting, and the site serving the ad. 

So, not only can you view the topics but also remove the ones you don’t wish and disable Topics altogether. You can also remove all the stored topics in your browser by clearing your browsing history or disable Topics API by entering the Incognito mode.

When Is Google Topics API Releasing?

As of now, there’s no date fixed for Topics API’s release. Google says that they are regularly working on it and performing rigorous testing to find flaws and fix them. It’s also taking feedback from across the globe and improving it.

So, let’s wait for the official announcement.


By the looks of what Google Topics API is offering currently, it certainly seems promising, with better privacy, transparency, and user control. Since privacy concerns are growing everywhere, this could prove to be a great initiative to preserve user privacy, giving users a choice of how they would like to see the ads served to them. 

Meanwhile, website owners and advertisers can also target the audience based on their interests instead of hitting random people with ads that may or may not be relevant. 

Hence, given the growing interest in Google Topics API, users, website owners, and advertisers are expected to witness wider adoption. 

You may also explore some top API management solutions for small businesses to enterprises.

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  • Amrita Pathak
    Amrita is a senior Technology Content Writer and Copywriter with a keen interest in delving deep into Cybersecurity, AI, ML, Cloud Computing, Web Hosting, Project Management, Software Development, and other topics on evolving technology….

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