The Privacy Sandbox is an initiative led by Google to create web standards for websites to access user information without compromising privacy. Its core purpose is to facilitate online advertising by sharing a subset of user private information without the use of third-party cookies. The initiative includes a number of proposals, many of these proposals have bird-themed names which are changed once the corresponding feature reaches general availability. The technology include Topics API (formerly Federated Learning of Cohorts or FLoC), Protected Audience, Attribution Reporting, Private Aggregation, Shared Storage and Fenced Frames as well as other proposed technologies. The project was announced in August 2019.
The initiative has been described as anti-competitive and has generated an antitrust response.
Privacy Sandbox will also be available on Android.
On September 7, 2023, Google announced general availability of Privacy Sandbox APIs, naming explicitly Topics, Protected Audience, Attribution Reporting, Private Aggregation, Shared Storage and Fenced Frames, meaning these features were enabled for more than half of Google Chrome users.
Model
Proposals in the Privacy Sandbox follow the idea of k-anonymity and are based on advertising to groups of people called cohorts instead of tracking individuals. They generally place the web browser in control of the user's privacy, moving some of the data collection and processing that facilitates advertising onto the user's device itself. There are three focuses within the Privacy Sandbox initiative: replacing the functionality of cross-site tracking, removing third-party cookies, and mitigating the risk of device fingerprinting.
Delivered technologies
Topics API
Topics API aims to provide the means for advertisers to show relevant content and ads by sharing interest-based categories, or ‘topics’, based on recent browsing history processed on the user device. Google Chrome, the only mainstream browser supporting Topics API as of September 2023, allows users to disable sharing of the interests via Topics API in browser's Settings.
Fenced Frames API
Fenced frames are an embedded frame type that is not permitted to communicate with a given host page, making it safe to access its unpartitioned storage as joining its identifier with the top site is impossible. FLEDGE-based will only be allowed to be displayed within Fenced Frames, although for the purpose of current testing it is still permissible.
Attribution Reporting API
The Attribution Reporting API facilitates conversion tracking, for example recording whenever an click on an ad or a view results in a purchase, while suppressing the ability to track users across multiple websites.
Protected Audience API
FLEDGE, which stands for "First Locally-Executed Decision over Groups Experiment", is a proposal that enables the targeting of interested audiences, including through retargeting. It allows vendors selected for advertising to take an advertiser’s website data and to place users in interest groups specifically defined for a given advertiser, meaning that users can see tailored ads, with no infringement on their privacy. On August 17, 2023, Google renamed FLEDGE as Protected Audience API since the API reached global availability.
Shared Storage API
Shared Storage API addresses a need for browsers, for legitimate cases, to store information in different, multiple, unpartitioned forms, rather than separately as the prevention of cross-site tracking generally dictates. Despite being unpartitioned, Shared Storage API ensures data can only be read in a secure environment.
Private Aggregation
Private Aggregation API tracks some aggregated statistics across ad campaigns.
Proposals
In January 2020, Google invited advertising technology companies to join the Improving Web Advertising Business Group (IWABG) of the World Wide Web Consortium (W3C) as a way to participate in the proposal process for the Privacy Sandbox. The IWABG is chaired by Wendy Seltzer. The W3C is a consensus-building organization and would not prevent Google from deploying technology without consensus.
Each proposal within the Privacy Sandbox initiative would perform one of the functions of targeted advertising that is currently done through cookies.