TikTok went dark for American users in an unprecedented display of the U.S.-China divide over technology and national security.The app started halting service Saturday night for 170 million users in its most important market shortly before a law took effect requiring it to shed its Chinese ownership or close in the U.

Starting today, when you open the TikTok app, you are greeted by a rather direct notice that the app is no longer available with a note about President-elect Trump

Even if temporary, the unprecedented shutdown of TikTok will have an impact on U.S.-China relations, domestic politics, the social-media marketplace and millions of Americans who depend on the app.