This 2022 experiment used a control group—roughly 10% of the app’s American user base at the time—who continued to receive content through an older version of the algorithm.
One participant in this group was 16-year-old Chase Nasca, who was served thousands of videos promoting suicide and self-harm before he took his own life.
The disclosure is significant because it highlights a deliberate trade-off between user safety and "stickiness," or the app’s ability to keep users active.
TikTok’s internal review noted that the decision was a "delicate balance" between safety and measuring impact on daily active users, a key metric for financial valuation.
This "by design" approach to product testing provides concrete evidence for ongoing mass litigation in U.S.
courts, where plaintiffs argue that social media platforms are inherently dangerous because they prioritize growth over the well-being of minors.
Moving forward, the document challenges previous testimony by TikTok executives regarding transparency and the platform's commitment to teen safety.
While TikTok has since suggested reducing the size and duration of such "backtests"—A/B experiments used to compare different versions of a product—internal warnings indicate that even smaller test pools would leave millions of users at risk of falling into "filter bubbles," or digital echo chambers of harmful content.
Although the company has settled several recent addiction lawsuits, this evidence remains a focal point in thousands of pending personal injury cases against major social media platforms.