Full Disclosure: Stress Testing Tech Platforms' Ad Repositories

Conducted with Check First, this research stress-tested and evaluated the usability of public ad-transparency repositories operated by 11 platforms and services — including Meta, Google/YouTube, TikTok, X, LinkedIn, Snapchat, Pinterest, Bing, Apple App Store, Booking.com and AliExpress — examining both technical robustness under load and how easily researchers and the public could actually use the tools.

The study found that transparency approaches vary widely across the platforms studied, and that even a technically sound repository can fail in practice if it is not user-friendly, limiting its value for oversight. Motivated by the EU Digital Services Act's requirement that very large online platforms maintain public ad libraries, the research treats these repositories as still-maturing tools rather than finished products.

While acknowledging genuine progress by the companies involved, the report does not find the current generation of tools fully adequate for reliably supporting independent scrutiny of advertising, and it offers recommendations for closing data gaps and inaccuracies rather than declaring the tools complete.