https://techcrunch.com/2021/03/15/signal-is-down-in-china/

Chinese users of the instant messenger Signal knew that the good times wouldn’t last long. The app, which is used for encrypted conversations, is unavailable in mainland China as of the morning of March 16, a test by TechCrunch shows. The website of the app has been banned in mainland China since March 15, according to censorship tracking website Greatfire.org.

Signal could not be immediately reached for comment.