The Signal Messenger app is displayed on a smartphone in Hong Kong, China.
Roy Liu | Bloomberg | Getty Images
GUANGZHOU, China – Encrypted messaging app Signal has stopped working in China and is now only accessible via a virtual private network (VPN).
China is blocking many foreign applications and services, including those of Facebook and Google. But Signal had not previously been barred by the so-called Great Firewall.
Signal claims to be end-to-end encrypted, meaning that the company itself and no outsiders can see the content of messages between a sender and the intended recipient. It also means that authorities cannot trace messages.
CNBC tested Signal on three different devices and messages did not go through, indicating that it was blocked by authorities. The app was still available to download via Apple’s China App Store.
Signal was not immediately available for comment when CNBC contacted him.
However, the messaging app still worked when used with a VPN. A VPN or virtual private network enables users to protect privacy and bypass Internet restrictions by connecting to servers around the world.
The signal blocked in China points to the growing censorship of the internet in the second largest economy in the world.
Signal downloads increased earlier this year after competitor WhatsApp changed its terms of service to enable data sharing with its parent company Facebook.
Signal is relatively small in China with 510,000 downloads so far from Apple’s App Store. But the app provides a rare way to send encrypted messages via a foreign platform without a VPN.
The dominant messaging app in China still remains TenC – owned WeChat, with more than a billion users.