Post a comment on Reddit, answer coding questions on Stack Overflow, edit a Wikipedia entry or share a baby photo on your public Facebook or Instagram feed and you are also helping to train the next generation of artificial intelligence.

TikTok and its bite-sized videos arrived in the United States as a global version of the Chinese app Douyin. Less than six years later, the social media platform is deeply woven into the fabric of American consumerism, having shortened the shelf life of trends and revamped how people engage with food and fashion.