Cloudflare is arguably the most popular content-delivery-network available today, and Cloudflare fronts more than 11.5 million webpages. Since Cloudflare is holding such a massive portion of internet traffic, the practices Cloudflare is utilizing affects millions of people's access to the internet and their privacy on the internet. Internet users have widely demonstrated Cloudflare's discriminatory practices against anonymous Tor users and web browsers on online forums and research papers. These practices limit or completely block webpages' functionality for "certain" users by implementing endless CAPTCHA loops. Therefore, the "Cloudflare CAPTCHA Monitoring" project aims to track how often Cloudflare fronted webpages return CAPTCHAs to Tor clients. The project achieves this by fetching webpages via both Tor and other mainstream web browsers and comparing the results. The tests are repeated periodically to find the patterns over time. Collected metadata, metrics, and results are analyzed and displayed on a public dashboard to understand how Cloudflare manipulates internet traffic and affects people's access to the internet.

Project page and documentation


Barkin Simsek


  • Georg Koppen
  • Roger Dingledine
  • Pili Guerra