Google Ad Topics: Another Cog in the Surveillance Advertising Machine

September 22, 2023 | Caroline Kraczon, EPIC Law Fellow

Internet users are constantly surveilled—advertisers collect and purchase mass volumes of consumer data and then use that data to serve highly targeted ads back to consumers. Surveillance advertising not only harms consumer privacy and autonomy by using highly personal data in ways that consumers do not expect; it also worsens inequity by enabling predatory and discriminatory ad targeting. EPIC has long advocated for consumer privacy, autonomy, and equity by pushing for greater legislative and regulatory protections for consumers from the harms caused by surveillance advertising.

In response to public pushback to surveillance advertising, some companies are implementing their own changes. Google is rolling out Ad Topics, its new framework for targeted advertising on Chrome. Ad Topics is part of Google’s Privacy Sandbox Initiative. Ad Topics was preceded by FLoC (Federated Learning of Cohorts), which would have organized users into groups based on their browsing history and served ads to users based on their assigned group. Google ended the FLoC project after facing criticism that the tool would harm user privacy and exacerbate discriminatory and predatory ad targeting. Google claims that Ad Topics incorporates feedback and criticism to the FLoC proposal, but the new system—like all “self-regulatory” approaches to privacy—fails to provide the systemic and reliable protections that consumers need.  

The implementation of Ad Topics plays a key role in Google’s plan to stop supporting third-party cookies on Chrome in 2024. Chrome will be the last major browser to stop supporting third-party cookies on its platform—Apple’s Safari began to block third party cookies by default in 2017, and Mozilla’s Firefox did the same in 2019. After falling behind its competitors and facing criticism for previous plans to phase out third-party cookies, Google now touts Ad Topics for its benefits to user privacy and transparency. But Google’s new tool is far from a perfect solution to the harms of surveillance advertising.

To implement Ad Topics, Chrome infers interest-based categories, called “topics,” by evaluating users’ browsing history. For example, some of the topics include Rap & Hip Hop Music, High Intensity Interval Training, Women’s Clothing, and Child Care. The Topics API assigns a topic label to websites based on the content of the website. Users are assigned a new topic associated with their most frequently visited websites each week. For example, if a Chrome user seeking a loan visited multiple online lending sites in a week, that user could be assigned the “Credit & Lending” topic. In the initial rollout of Ad Topics, only 469 broad topics are included, but the topic taxonomy could expand in the future. Google states that it “aims to maintain a topics list that does not include sensitive categories (i.e. race, sexual orientation, religion, etc.).” Chrome will automatically delete topics after four weeks. Google states that topics are selected locally on users’ devices and that users’ topic data is not shared to external servers. To use topic data to serve an ad, Chrome shares the user’s topics with websites the user visits, and website may serve an ad related to one of the user’s topics.

The Ad Topics program does introduce some notable privacy features and changes. First, Chrome permits users to view their assigned topics. Users may block certain topics, which prevents Chrome from sharing that topic with websites the user visits. Users may also opt out of Ad Topics altogether within their account settings.

Second, a major privacy concern cited by advocates when Google was considering the FLoC project was the risk of browser fingerprinting, which is the practice of gathering data from a user’s browser to create a unique identifier, or “fingerprint,” of the browser. Dividing users into a relatively small number of groups, which the FLoC project would have done, would have made fingerprinting much easier for third parties. Google has stated that Ad Topics reduces the risk of fingerprinting because the assigned Topics are broad, and users are assigned multiple Topics at once. But Ad Topics has not been implemented on a large scale yet, so it remains to be seen whether Google’s changes will significantly diminish the threat of fingerprinting for users. Further, while Google’s plan to end support for third-party cookies limits one source of data that could be used to reidentify users, first party data—data that users provide to websites or that websites collect about their users—could still be combined with Ad Topics data to reidentify users. Additionally, Google has yet to fully implement other major proposals put forward to limit covert tracking of Chrome users, such as Privacy Budget.

Third, Ad Topics may in some respects be a privacy improvement compared to third-party cookies, which are small text files placed onto a user’s computer by a party other than the website the user chooses to visit. These cookies follow users around the internet, remembering their previous activities and providing detailed information about the user’s browsing history to advertisers. In comparison to third-party cookies, Ad Topics has potential to increase privacy and transparency for users.

All that said, users should not have to trust Google to implement a better solution to ad targeting than third-party cookies, especially considering that the company has already fallen short of its promises for Ad Topics. One of Google’s primary claims in support of Ad Topics is that the tool empowers user choice, but Google has automatically opted U.S. Chrome users into Topics. Users likely do not even know that the tool has been enabled, let alone know the process to opt out in Chrome’s settings. In terms of privacy, Ad Topics will continue to constantly surveil users’ online activity and then use the product of that surveillance to target ads to users, which may result in discrimination and predatory ad targeting. Google promises that it will aim not to include sensitive classifications in the topic list, but the company has failed to provide any details about how it will expand the topic taxonomy and evaluate whether any of the topics it includes on the list is a proxy for a sensitive characteristic or has a disparate impact on marginalized groups.

Whatever privacy gains Ad Topics may bring, Google’s new system poses the same privacy, discrimination, and predatory targeting risks as previous surveillance advertising architecture. Google is currently under pressure to publicly support user privacy and turn off third-party cookies on Chrome, but the company is doing so in a way that only gives them more control over user data. Ad Topics restricts third parties from using Chrome users’ data, but Google itself retains control over the surveillance advertising lifecycle on Chrome—from data collection to ad targeting. The company has been under scrutiny for its anticompetitive advertising practices in Europe, and the company is also currently on trial in an antitrust suit against the Justice Department. Whatever arguable privacy benefits it may bring, Ad Topics is another example of Google’s attempts to silo user data for its own benefits.

Google is an online advertising giant, making $224 billion in ad revenue in 2022. Companies that profit from the collection and sale of personal data are often not incentivized to push forward meaningful privacy reforms, nor can we trust the integrity and durability of any reforms those companies make absent robust legal safeguards. Given the serious harms imposed by surveillance advertising, internet users deserve meaningful and systemic protections. For example, EPIC has previously supported a ban on surveillance advertising and has urged the FTC to promulgate rules to protect consumers from harms caused by commercial surveillance.

Chrome users wishing to opt out of Ad Topics should do so by following the steps below:

  1. Open Chrome on your device
  2. At the top right, click More > Settings
  3. From the menu on the left, click Privacy and Security
  4. Click Ad Privacy
  5. Click Ad Topics
  6. Toggle Ad Topics to Off or Block certain topics from your topics list

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