Pro-democracy protestors in Hong Kong continue to rally against China's limitation of voter rights. And while the fact that they have turned to technology to ensure their voices are heard isn't particularly new, one tool they're using in record numbers is.

Firechat has seen a whopping 210,000 downloads over a two-day span, propelling the title to the number one app overall in Hong Kong on both iOS and Android. Over those two days, more than 2 million chat sessions were initiated, each lasting just over three and a half minutes on average (most folks normally spend closer to one minute in an app on average, so that's some dedicated engagement). With peaks hitting up to 35,000, Firechat is regularly seeing up to 20,000 concurrent app users in the area, which is about the same usage as you might see in a popular game.

And these numbers are only conservative estimates, Open Garden (the company behind Firechat) CMO Christophe Daligault told WIRED. They can only get analytics from users who are connected to the internet. They have no data on how many more folks are using the app completely off the grid.

Firechat Josh Valcarcel / WIRED

Firechat is a peer-to-peer framework that allows for wireless mesh networking. It lets you communicate regardless of whether you have a data connection or not by connecting nearby devices to one another over Bluetooth, Wi-Fi networks, or peer-to-peer Wi-Fi. While Firechat is currently adding verified accounts to the service, you can use the app anonymously, which makes it especially helpful in situations like what's happening in Hong Kong, when police could be looking to identify and apprehend protest organizers.

The massive uptick began Sunday afternoon, fueled by two main reasons: fear that internet access may be shut down (which has not happened yet) and because of cellular network congestion, which is making it difficult for students to use any other app for communicating, especially since China elected to block some social networks, like Instagram.

This isn’t the first time Firechat has seen its off-the-grid communication network peak. In May, Iranians turned to Firechat as Whatsapp and Instagram were blocked. And in June, Firechat gained popularity in Iraq when internet access was shut down in some areas. In March, the Sunflower student movement in Taiwan saw the most Firechat usage the app had seen to date, until now—the situation in Hong Kong is providing 25 times the traffic as Taiwan.