The Signal Messenger app is displayed on a smartphone in Hong Kong, China.
Roy Liu | Bloomberg | Getty Images
GUANGZHOU, China – The Signal encrypted messaging app has stopped working in China and can now only be accessed via a virtual private network (VPN).
China blocks many foreign applications and services, including those from Facebook and Google. But Signal had not previously been stopped by the so-called Great Firewall.
The signal claims to be encrypted from end to end, which means that neither the company itself nor third parties can view the content of messages between a sender and the intended recipient. It also means that the authorities cannot spy on messages.
CNBC tested the signal on three different devices and the messages were not transmitted, suggesting that it was blocked by the authorities. The app was still available for download from Apple’s China App Store.
Signal was not immediately available for comment when contacted by CNBC.
The messaging app, however, still worked when used with a VPN. A VPN or virtual private network allows users to protect privacy and bypass Internet restrictions by connecting to servers around the world.
The signal block in China highlights the growing censorship of the Internet in the second largest economy in the world.
Signal downloads increased earlier this year after rival WhatsApp changed its terms of service to allow some data to be shared with its parent company, Facebook.
The signal is relatively small in China, with 510,000 downloads so far from Apple’s App Store, according to Sensor Tower. But the app has provided a rare way to send encrypted messages over a foreign platform without a VPN.
Still, the dominant messaging app in China remains Tencent-owned WeChat, with more than a billion users.