Browser tracking cookies are small pieces of data that websites store on users’ devices to remember their preferences, login details, and online behavior. They are also used by advertisers to track users across different websites and show them personalized ads based on their interests and browsing history.
However, tracking cookies have raised privacy concerns among users, regulators, and advocates, who argue that they enable intrusive and unwanted surveillance of online activity. Some browsers, such as Safari and Firefox, have already blocked third-party cookies by default, limiting the ability of advertisers to reach their audiences and measure the effectiveness of their campaigns.
Google, which owns the most popular browser in the world, Chrome, has announced a different approach to address the privacy issues of tracking cookies. Instead of blocking them outright, Google plans to replace them with a new set of features called the Privacy Sandbox, which aims to provide a balance between user privacy and web advertising.
The Privacy Sandbox is a collection of proposals that Google is developing and testing with the web community, including publishers, advertisers, developers, and browsers. The main idea is to use anonymized and aggregated data to create groups of users with similar interests, called cohorts, and use them as signals for ad targeting and measurement, instead of individual identifiers.
One of the key proposals in the Privacy Sandbox is the Federated Learning of Cohorts (FLoC), which uses machine learning to cluster users into cohorts based on their browsing behavior. Each cohort is assigned a unique ID, which is shared with websites and advertisers, but does not reveal any personal or sensitive information about the users. According to Google, FLoC can provide an effective replacement for third-party cookies, delivering at least 95% of the conversions per dollar spent compared to cookie-based advertising.
Another proposal is the FLEDGE (First Locally-Executed Decision over Groups Experiment), which allows advertisers to create and deploy their own audiences using first-party data, such as email lists or website visitors, without the use of third-party cookies. FLEDGE uses a secure and isolated environment, called a trusty, to store and process the audience data on the user’s device, and to run the ad auction and selection.
Google claims that the Privacy Sandbox will offer a privacy-first and user-centric solution for web advertising, while also preserving the viability and sustainability of the web ecosystem. However, the Privacy Sandbox has also faced criticism and scrutiny from various stakeholders, who question its feasibility, effectiveness, and impact on competition and innovation.
Google expects to phase out support for third-party cookies in Chrome by mid-2023, after testing and refining the Privacy Sandbox features with the web community. The Privacy Sandbox is a complex and ambitious project that will likely have significant implications for the future of the web, both for users and businesses.