TikTok’s powerful algorithm is exceptionally good at engaging users. But what happens when the endless scroll on the app turns into a stream of potentially harmful content, including on starvation diets, self-harm and suicide? And why do users who say they didn't go looking for this type of content still see so much of it? This is the first part of Tech News Briefing’s special three-part series looking at the real-life impact of social-media spirals. Learn more about your ad choices. Visit megaphone.fm/adchoices