Trump Joins TikTok, the App He Once Tried to Ban

Donald J. Trump has joined TikTok, the social media app that he tried to ban during his presidency but that he more recently has embraced as he and his campaign try to reach younger voters before November’s general election.

Mr. Trump’s account shared its first video on Saturday night, when he attended an Ultimate Fighting Championship bout in New Jersey. In the post, Mr. Trump stands in the bowels of an arena next to Dana White, the U.F.C. chief executive. “The president is now on TikTok,” Mr. White says.

“It’s an honor,” Mr. Trump responds, a striking change of tune from his efforts to ban the app through an executive order over national security concerns.

Then, the video, just 13 seconds long, cuts to clips of Mr. Trump walking into the packed arena and receiving a raucous and warm reception from U.F.C. fans while Kid Rock’s song “American Bad Ass” plays in the background.

Mr. Trump’s inaugural post is largely an extension of his campaign’s efforts on social media to amplify the hero’s welcome he often gets at U.F.C. fights, where the largely young and male audience tends to overlap with his base.

But his decision to join TikTok was a striking turnabout in his views of the social video app, which has roughly 170 million American users and an audience that skews younger than those of other social media platforms.