The largest collection of public internet censorship data ever compiled shows that even citizens of what are considered the world’s freest countries aren’t safe from internet censorship.

A team from the University of Michigan used its own Censored Planet tool, an automated censorship tracking system launched in 2018, to collect more than 21 billion measurements over 20 months in 221 countries.

“We hope that the continued publication of Censored Planet data will enable researchers to continuously monitor the deployment of network interference technologies, track policy changes in censoring nations, and better understand the targets of interference,” said Roya Ensafi, U-M assistant professor of electrical engineering and computer science who led the development of the tool.