It's been a tense few days in Hong Kong as protesters fight for democracy. Demonstrations have been peaceful but they require a lot of effort to organize. With the looming threat that Internet or cellular connection may be cut off by the government, protesters turned to FireChat to ensure communication lines remain open.

What is FireChat? Essentially, it is a messaging app that doesn't need Internet or cellular access to work. When traditional connections are not available, FireChat connects users through Bluetooth, creating a mesh network that grows stronger as more users join it.

Over the weekend, FireChat was downloaded more than 100,000 times in Hong Kong in response to student activist Joshua Wong's encouragement. He took to Twitter and Facebook, telling people to download the app just in case the authorities decide to cut off Internet and cellular connection in the area.

Internet and cellular access remain available, but many are complaining about slower network speeds because of congestion. This can't be helped given the number of people converging for the pro-democracy protest.

But while Internet and cellular connections remain open, Beijing has censored social networking sites to prevent references about the demonstrations from reaching the mainland. Aside from censoring popular microblogging service Sina Weibo, authorities were also assumed to have blocked Instagram. Facebook has been inaccessible since 2009 after it was blocked during the Xinjiang riots.

It is not clear how many people are using FireChat exactly to communicate during protests, but just the number of downloads recorded during the weekend is a good place to start.

While the app is seeing its biggest numbers in Hong Kong, this isn't the first time, though, that FireChat was utilized in this kind of setting. Just 10 days after it was released in March, the Sunflower Movement in Taiwan also turned to FireChat to protect their lines of communication. At the time, Taiwanese students were protesting a trade deal involving China.

FireChat also saw a spike in downloads when the Iranian government prevented access to WhatsApp and Instagram in May.

"People in Hong Kong who are protesting for democracy are able to use FireChat in a way that helps fight oppression against their Internet use. We can't solve their problems, but at least we can help with communication," said Stanislav Shalunov, Open Garden co-founder. Open Garden developed FireChat.