The subscription fees charged by academic publishers have risen so high in recent years that even wealthy American universities have said they can’t afford them. When Harvard Library reported its subscription costs had reached $3.5 million per year in a 2012 memo, for example, it said the fees were “fiscally unsustainable,” and the university asked its faculty to stop publishing research in journals that keep articles behind paywalls.

But regardless of where Harvard researchers have published their work since then, it’s likely that all of it is currently available for free on Sci-Hub, a rogue pirating service for academic research. According to a new study, Sci-Hub contains 68.9% of all academic research. More to the point: 85.2% of all papers originally published behind paywalls are available on the website for free. And even if a given article isn’t already available in Sci-Hub’s repository, the site can quickly fetch it using donated credentials for services like JSTOR, Elsevier, and Sage.

Sci-Hub was founded in 2011 by Alexandra Elbakyan, a Kazakh national who lives in Russia. The website, originally at sci-hub.org, has been forced by court orders and law enforcement to change its domain address several times, and is now available on the dark web and over the encrypted messaging app Telegram. The operation is primarily funded through bitcoin donations.

Data scientist Daniel Himmelstein of the University of Pennsylvania, who conducted the new study, concluded that Sci-Hub’s extensive catalogue is making the subscription publishing model “unsustainable.”

“For the first time, the overwhelming majority of scholarly literature is available gratis to anyone with an Internet connection,” he writes.

That’s as it should be, advocates of open research say. They argue, among other things, that a substantial portion of the research that publishers attempt to lock behind paywalls was funded with grants paid for by taxpayers, and that the public should therefore have unfettered access to it.

Meanwhile, the publishers aren’t going down without a fight. The publisher Elsevier sued Sci-Hub, claiming copyright infringement, in 2011—and a New York district court ruled last month that Elsevier is owed $15 million in damages.