TikTok's Alex Zhu is trying to broaden the app's appeal from its predominantly 13 and younger fans to expand its audience and risk becoming "a passing fad," write Georgia Wells and Yoree Koh in The Wall Street Journal. Recent moves include rejecting content that might appear "too juvenile," preventing the use of childish animated graphics and using artificial intelligence to detect a user's age, which appears to be working as #over30, #over40 and #MomsOfTikTok started trending in early 2019.