The Signal Messenger app is displayed on a smartphone in Hong Kong, China.
Roy Liu | Bloomberg | Getty images
GUANGZHOU, China – Encrypted messaging app Signal no longer works in China and can now only be accessed through a virtual private network (VPN).
China blocks many foreign apps and services, including those from Facebook and Google. But Signal was not previously blocked by the so-called Great Firewall.
Signal claims to be end-to-end encrypted, meaning that neither the company itself nor any outsider can see the content of messages between a sender and the intended recipient. This also means that authorities cannot snoop on messages.
CNBC tested Signal on three different devices and messages failed, suggesting it has been blocked by 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.
However, the messaging app still worked when used with a VPN. With a VPN or virtual private network, users can protect privacy and bypass internet restrictions by connecting to servers around the world.
Signal being blocked in China highlights increasing internet censorship in the world’s second largest economy.
Signal downloads rose earlier this year after rival WhatsApp changed its terms of service to allow sharing of certain data with parent company Facebook.
Signal is relatively small in China with 510,000 downloads from Apple’s App Store to date, according to Sensor Tower. But the app offered a rare way to send encrypted messages over a foreign platform without a VPN.
Still, the dominant messaging app in China remains WeChat, owned by Tencent, with more than a billion users.