When thousands of pages started disappearing from the Centers for Disease Control and Prevention (CDC) website late last week, public health researchers quickly moved to archive deleted public health data.

Soon, researchers discovered that the Internet Archive (IA) offers one of the most effective ways to both preserve online data and track changes on government websites. For decades, IA crawlers have collected snapshots of the public Internet, making it easier to compare current versions of websites to historic versions. And IA also allows users to upload digital materials to further expand the web archive. Both aspects of the archive immediately proved useful to researchers assessing how much data the public risked losing during a rapid purge following a pair of President Trump’s executive orders.

Part of a small group of researchers who managed to download the entire CDC website within days, virologist Angela Rasmussen helped create a public resource that combines CDC website information with deleted CDC datasets. Those datasets, many of which were previously in the public domain for years, were uploaded to IA by an anonymous user, “SheWhoExists,” on January 31. Moving forward, Rasmussen told Ars that IA will likely remain a go-to tool for researchers attempting to closely monitor for any unexpected changes in access to public data.

Rasmussen told Ars that the deletion of CDC datasets is “extremely alarming” and “not normal.” While some deleted pages have since been restored in altered versions, removing gender ideology from CDC guidance could put Americans at heightened risk. That’s another emerging problem that IA’s snapshots could help researchers and health professionals resolve.

On Bluesky, Rasmussen led one of many charges to compile archived links and download CDC data so that researchers can reference every available government study when advancing public health knowledge.

“These data are public and they are ours,” Rasmussen posted. “Deletion disobedience is one way to fight back.”

To help researchers quickly access the missing data, anyone can help the IA seed the datasets, the Reddit user said in another post providing seeding and mirroring instructions. Currently dozens are seeding it for a couple hundred peers.

“Thank you to everyone who requested this important data, and particularly to those who have offered to mirror it,” the Reddit user wrote.

As Rasmussen works with her group to make their archive more user-friendly, her plan is to help as many researchers as possible fight back against data deletion by continuing to reference deleted data in their research. She suggested that effort—doing science that ignores Trump’s executive orders—is perhaps a more powerful way to resist and defend public health data than joining in loud protests, which many researchers based in the US (and perhaps relying on federal funding) may not be able to afford to do.

“Just by doing things and standing up for science with your actions, rather than your words, you can really make, I think, a big difference,” Rasmussen said.