#114 · Find · 10/10/2026

How PrivacyTests.org evaluates browser privacy

An overview of Arthur Edelstein's automated browser testing project, its methodology for measuring data isolation, new developments for Chrome users, and existing gaps in the published documentation.

PrivacyTests.org subjects popular web browsers to automated leak tests and publishes comparative results online for public inspection. When evaluating these browsers, the site conducts state partitioning tests to determine whether a browser isolates website data to prevent tracking companies from sharing identifying state across different sites. Browsers that successfully protect against a specific data leak receive a green indicator, while confirmed data leaks are marked with a red indicator. To support open verification, anyone can clone the project's git repository and execute the browser tests independently. Beyond this testing suite, development is currently underway for Privacy Magic, a set-and-forget browser privacy extension designed specifically for Chrome.

According to statements provided by Arthur Edelstein, PrivacyTests.org operates as an independent project that he created and launched to the public in 2021, following his prior work on browser privacy at the Tor Project, Mozilla, and Brave. However, these background details and the project's operational independence remain disputed, with an external research report raising potential concerns regarding Edelstein's previous background at Brave Software. Additionally, claims that the underlying source code and testing suites are licensed under the MIT license are formally disputed. Disagreement also surrounds the specific security risk posed by unpartitioned Alt-Svc settings, which some sources contend could allow cross-site user tracking.

The project's testing framework matters because it evaluates how default, out-of-the-box browser configurations perform when attempting to stop cross-site data sharing. By assigning binary green and red indicators based on automated leak detection, the comparative results offer a direct way to view which default settings actively restrict tracking companies. The ongoing construction of Privacy Magic extends this focus directly to Chrome users by offering a simple extension designed to manage privacy settings without complex manual intervention.

An external research report noted potential concerns regarding the creator's historical ties to Brave Software, though official excerpts maintain that the venture is operated independently and published as open-source material. Other analytical caveats emphasize that the site's evaluations are strictly limited to out-of-the-box defaults. Consequently, the published test scores do not account for third-party extensions or custom user-hardened configurations that individual users might apply to enhance their baseline privacy protection.

It remains unknown how frequently the automated test suites are executed across all published browsers, as the project's official documentation does not specify a precise update schedule. It is also unclear to what extent user-hardened settings or supplemental privacy extensions would alter the specific red and green leak indicators generated during default testing.