What Is Google Topics API?

Brock Munro
May 1, 2024
June 14, 2024
What Is Google Topics API?

After 2024, publishers may not be able to rely on third-party cookies for targeted ads anymore. Since 2019, Google has been trying to provide viable alternatives to third-party cookies through its Privacy Sandbox initiative. 

A core component of Google’s vision for a cookie-free future is Topics API.

It is an improvement over Google’s previous solution to third-party cookies—Federated Learning of Cohorts (FLoC), in that it is designed to be even more protective of users’ identities.

For publishers seeking alternatives to third-party tracking that does not invade user privacy, it is important to acquire a good understanding of Topics API.

In this in-depth post, we present answers to the most common questions about Topics API—what it is, how it works, why Google replaced FLoC with Topics API, and what is the potential impact of Topics API on publishers.

What Is Google Topics API?

Topics API is a mechanism in Google Chrome’s Privacy Sandbox initiative that allows web browsers to share a user’s topics of interest with third-party publishers and advertisers while protecting their privacy and online browsing history.

Thus, rather than detailed user information, what gets collected and shared with third-party entities are coarse-grained interest signals inferred from a user’s most recent online interactions.

The advantage of Topics API is that it enables interest based advertising without the need to closely track all the websites a user visits and store their personal information, including potentially sensitive data, the way third-party cookies did.

Google unveiled Topics in January 2022 as a replacement for its Federated Learning of Cohorts (FLoC) standard. With the impending death of third-party cookies, Google is positioning Topics API as an alternative that boosts privacy by focusing on the general interests of users.

How Does Google Topics API Work?

Topics API works by observing topics that may be of interest to users based on their recent browsing history, and sharing these with an API caller such as an adtech platform.

 Here’s a step-wise breakdown of how this process unfolds:

  1. A user’s browser observes the topics they are interested in based on the websites they visit within a specified period of time known as an epoch. At present, Google has set the epoch for most users at one week.
  2. The Topics API then organizes these topics within hierarchical categories known as taxonomies. These are based on pre-defined interest clusters such as arts and entertainment, computers, pets and animals, etc. At present, Chrome has an initial taxonomy amounting to some 469 categories with plans to increase them further. 
  3. Topics API then calculates the most popular topics for each user within an epoch.
  4. When a user visits a website that has enabled Topics, the API shares handpicked topics from the most recent epoch with the website’s adtech platform.
  5. The adtech platform then displays contextual ads based on these topics.

The system has multiple features in place to improve user privacy and provide greater control over how the data is handled. These include:

  1. It does not send any user data to external servers.
  2. Topics are deleted after three weeks.
  3. Users have the option to disable the feature completely.
  4. Users can also view selected topics and delete them. For instance, Chrome users can click on the three dots menu on the top right corner of their screen, go to Settings, and click on Privacy and Security. They can then tap the Ad Privacy tab and go to Ad Topics to view which topics are being shared by Chrome with other websites. Any topics they don’t want shared with third-parties can be blocked or deleted.
  5. Topics are human curated to exclude sensitive categories such as gender, sexual orientation, and race.

What Is FLoC?

Federated Learning of Cohorts (FLoC) was the predecessor to Topic API in Google’s Privacy Sandbox initiative. It was launched by Google in 2021 as a privacy-friendly alternative to third-party cookies.

Third-party cookies work by storing user data every time a user visits a website, then sharing it among different entities such as demand side partners (DSPs) and data management platforms (DMPs) to ensure that a user and their interests are correctly identified. This process, known as cookie syncing, allowed a relatively accurate matching of user interests with ads displayed to them. However, it also raised privacy concerns relating to the storing of user data, and its sharing across multiple entities.

FLoC attempted to overcome this issue by using cohorts instead of individual users as the basic unit of data collection. Thus, instead of targeting individual users, ads would now target groups of users having  similar interests.

Here is an example to explain how FLoC was designed to work:

  1. The browser tracks a user’s browsing activity and classifies their interests into categories such as tech, video games, sports, etc.
  2. An algorithm then places users in a cohort with other users who have similar interests and assign this group a Cohort ID.
  3. Publishers and advertisers get access only to the Cohort ID to generate targeted ads relevant to the cohort’s interests.
  4. The FLoC algorithm updates every week such that if a user’s browsing behavior changes after a week, they may be placed in a different cohort.

Why Did Google Pull the Plug on FLoC?

Although Google touted privacy as the main advantage of FLoC, the standard ultimately failed to live up to its promise. FLoC faced heavy criticism from leading privacy-focused organizations like the Electronic Frontier Foundation (EFF) and Mozilla. They cited the following main privacy risks:

  1. Fingerprinting: Cohorts can make it easier for trackers to create a unique identifier based on browsing habits. This process is called fingerprinting
  2. Discrimination: The unsupervised algorithm may create cohorts based on sensitive factors like age, race, and income, with the potential for discriminatory targeting.
  3. Other Privacy Concerns: Companies that already have first-party data on the user can use cohort IDs to collect unauthorized data about their users.

As a result of the backlash, Google retired FLoC after its origin trials and announced Topics API as the replacement in January 2022.

Google Topics API vs Third Party Cookies 

Topics API primarily differs from third-party cookies in that it only collects and shares information relating a user’s areas of interests without sharing any additional information. Here’s a detailed comparison to explain how Topics API is an improvement over third-party cookies.

Third-Party Cookies Google Topics API
User data privacy concerns Since they collect and store detailed browsing history and other user data, cookies have major privacy concerns Topics API does not track or store detailed browsing histories and has fewer privacy concerns.
User control and consent Does not have adequate privacy control options. Comes with the option to review and delete topics, and even opt out of the system altogether
Ad targeting accuracy Relatively precise and personalized targeting is possible. Since it relies on general interest topics, publishers can expect less precise ad targeting.
Compliance with regulations Limited compliance as newer regulations like GDPR and CCPA target third-party cookies. Greater degree of compliance with most privacy regulations currently in force
Relevance and viability Widely seen as inconsistent with user expectations regarding privacy. Further, they have little to no future viability due to planned phase-outs by Google and Apple. Was developed in response to pressure from users and regulators, and represents Google's plans for the future of digital advertising
Impact on Publisher Revenues As an established and convenient method, cookies made it easier for publishers to generate revenues through precise targeting. The full extent of the impact of Topics API on publisher revenues is still not clear.

Google Topics API vs FLoC

The primary difference between FLoC and Topics API is that where FLoC uses the cohort as the basic unit of data collection and targeting, Topics uses the user’s interests for the same. In other words, where FLoC attempted to ensure privacy by anonymizing the user into a cohort, Topics attempts to protect user privacy by anonymizing the user’s interests into broad-based topics. 

Here’s a detailed comparison of the differences between the two.

Third-Party Cookies Google Topics API
User data privacy concerns Since they collect and store detailed browsing history and other user data, cookies have major privacy concerns Topics API does not track or store detailed browsing histories and has fewer privacy concerns.
User control and consent Does not have adequate privacy control options. Comes with the option to review and delete topics, and even opt out of the system altogether
Ad targeting accuracy Relatively precise and personalized targeting is possible. Since it relies on general interest topics, publishers can expect less precise ad targeting.
Compliance with regulations Limited compliance as newer regulations like GDPR and CCPA target third-party cookies. Greater degree of compliance with most privacy regulations currently in force
Relevance and viability Widely seen as inconsistent with user expectations regarding privacy. Further, they have little to no future viability due to planned phase-outs by Google and Apple. Was developed in response to pressure from users and regulators, and represents Google's plans for the future of digital advertising
Impact on Publisher Revenues As an established and convenient method, cookies made it easier for publishers to generate revenues through precise targeting. The full extent of the impact of Topics API on publisher revenues is still not clear.

Potential Impact of Topics API for Publishers

The phasing out of third-party cookies has left a void in the adtech space for which a universally agreed upon solution is yet to be found. While Topics API is an important alternative, it is far from the only one.

According to the latest surveys by Interactive Advertising Bureau (IAB) Europe (PDF download), the majority of publishers are testing contextual advertising (63%), first-party identifiers (60%), and authentication-based identifiers (56%) as alternatives to third-party cookies. Only 43% were testing Privacy Sandbox APIs like Topics.

Uncertainty, limited testing time, and expectations of weak results are major reasons why publishers are not too enthusiastic about Topics API and other Sandbox features.

With limited adoption and a largely fragmented market, it is not easy to measure or forecast the potential impact of Topics API on publishers, particularly in terms of revenues. However, we can still speculate on the following pros and cons:

Possible Advantages of Topics API

  • Allows publishers to identify user interests for more personalized ad targeting without causing significant privacy risks.
  • Broad topics may benefit larger publishers who have more diverse content across their sites.
  • Is relatively easier to implement than other previous Privacy Sandbox options like FLoC.

Possible Disadvantages of Topics API

  • The additional focus on privacy and randomization may impact the accuracy of ads and reduce ad revenues.
  • Since it lacks the granular targeting capabilities of third-party cookies, it may severely affect small, niche publishers. 

Future of Google Topics API

Topics API was launched in July 2023. Till date, both Mozilla Foundation (Firefox browser) and Apple (Safari) have refused to adopt Topics API citing a host of potential privacy concerns.

A major issue for many critics is the potential for fingerprinting that ill-intentioned actors can exploit. Even Google seems to recognize this risk. Before enrolling for the API, developers have to explicitly attest that they will not abuse Topics API to violate user privacy.

While that is not a reliable solution to the problem, Google has few other options. Since they cannot postpone the deprecation of cookies beyond 2024, Google decided to move forward with Topics API and hoped that they could iron out its issues and gain the acceptance of other browsers.

However, the approach may still have some relevance in a cookie-less future, as publishers will have to rely on multiple strategies to sustain revenues while complying with user privacy regulations. 

For instance, Topics API can be combined with an increased reliance on the use of first-party cookies for targeting. For those not sure of the difference between the two types of cookies, we’ve created this detailed guide on first-party vs third-party cookies that explains the differences between the two in detail.

Final Thoughts

Topics API is one among the many third-party cookie alternatives vying for supremacy in a cookie-less world. While it offers major privacy improvements over third-party cookies and FLoC, Topics API is not without its own limitations.

Publishers may need to get creative and come up with multi-pronged strategies to adapt to a future without third-party cookies. 

For publishers looking to gain access to a wider range of premium ad partners, Publift offers a suite of tailored solutions designed to maximize their ad revenue. As a Google Certified Publishing Partner, Publift has helped its partners realize an average of 55% uplift in revenue. 

Book a demo today to learn more about how we can help you prepare for a cookie-less future.

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