When pro-democracy protests erupted in Hong Kong late last month, many demonstrators feared the government would shut down the internet. Those fears never materialized, but the specter of a crackdown combined with congested data networks were enough to drive thousands to download FireChat — a smartphone application that lets users communicate without an internet connection.

The app, which launched in March, has seen 500,000 downloads in Hong Kong since protests began on September 27th, driving it to the top spot on the Apple App Store and Google Play in Hong Kong. At its peak, FireChat saw 37,000 simultaneous users, each spending, on average, more than two and a half minutes on the app — and that’s not counting those who used the app offline.

"Our first reaction was okay, let's hope it works. And it did," says Christophe Daligault, chief marketing officer at Open Garden, the San Francisco-based company that developed FireChat. The last two weeks have been a whirlwind for Open Garden, which designed FireChat with festivals, technology conferences, and other events in mind — not necessarily protests. "Most of us haven't slept much at all," Daligault adds.

Unlike WhatsApp and other messaging apps, FireChat doesn’t require an internet connection for users to communicate. Instead, it uses a phone’s Bluetooth and Wi-Fi signals to connect it to other devices within a given range. In this setup, known as a mesh network, each phone acts as a node, and as more devices link together, the network’s range expands. Users can send texts and images under pseudonyms — another benefit for government-fearing protesters — though Open Garden recently introduced verified accounts for some journalists.

The app gained attention at this year’s Burning Man festival, where attendees used it to organize and coordinate events in the middle of the Nevada desert, though it’s also been used in countries like Iran and Iraq, where the internet is aggressively censored, and during this year’s protests in Taiwan. But nothing compares to the flood of downloads it saw in Hong Kong — something that took Open Garden by surprise.

"We had no idea that it was going to be popular in those places," Daligault says. FireChat was created, he explains, with two use cases in mind: the developing world, where data plans are often prohibitively expensive, and live events or festivals, where cellular networks are usually congested and slow.

"FireChat is not a tool for private communications."

Ping Wong, secretary general of the Internet Society Hong Kong, was in Hong Kong as the demonstrations unfurled, and watched as chatrooms buzzed on FireChat. She says that many protesters continued to use Facebook and WhatsApp to coordinate events, whereas most messages sent on FireChat were "reporting what’s happening in real-time, like where the police are and what they are doing," or calls for supplies like food and water. Laurel Chor, who covered the protests for the news site Coconuts Hong Kong, says FireChat wasn't as ubiquitous as other social-networking apps, though several demonstrators told her that it helped distinguish rumor from truth.

The app's sudden popularity in Hong Kong has spurred downloads in other parts of the world, though it was never explicitly conceived as a protest tool. In fact, there are no real safeguards against government surveillance — a point that Daligault is quick to emphasize. "FireChat is not a tool for private communications," Open Garden wrote in a Tumblr post this month. "People who use Twitter understand that their communications are public. They can use pseudonyms and know that what they tweet may be seen by other people. It is the same with FireChat."

Chatting under pseudonyms may offer a sense of protection to protesters, though the app was never designed to guarantee anonymity. "FireChat provides more or less about the same extent of identity protection as Twitter or Instagram," Stanislav Shalunov, Open Garden co-founder and CTO, said in an email. "It is not specifically designed to provide some absolute protection of the user's identity."

"I believe the government may be monitoring communications on FireChat, so as to know what's happening," Wong says. "But I don't think the protesters fear the monitoring. Maybe you can say it is expected."

Encrypted private messaging is in the works

The company plans to eventually introduce encrypted private messaging, though it’s not on the immediate horizon. On the surface, it would seem as if private messaging would threaten the openness that FireChat’s networks depend upon, but Daligault envisions the service as an add-on to the public chats, and believes it will actually expand the app’s user base in the long run.

FireChat's download rates declined when protests began dwindling in Hong Kong last week, though Daligault says there's been no significant slowdown in activity. Tensions escalated once again this week, after government leaders abruptly cancelled negotiations with protesters, and flared on Wednesday, after video of a protester being beaten by police began spreading across the internet.

It's not clear whether FireChat's popularity will sustain once things calm down in Hong Kong — the government said Thursday that it's ready to begin negotiations with student protesters — though Open Garden hopes its app will eventually extend beyond the realm of protests and civil unrest.

"I wish the app was known for other things," Daligault says, "but so it is."