A Los Angeles jury has found Instagram and YouTube deliberately designed to be addictive and negligent in protecting a young user, awarding $6m (about £4.5m) to the plaintiff known as Kaley.
The woman told the court the platforms left her with body dysmorphia, depression and suicidal thoughts.
Meta and Google say they will appeal — Meta argues a single app cannot be held solely responsible for a youth mental health crisis, and Google disputes classifying YouTube as a social network.
Legal experts say the decision could be a watershed moment for social media regulation.
A US law professor described the ruling as an end to a long period of legal immunity for platforms, and observers compare the shift to earlier public-health reckonings with other industries.
TikTok and Snapchat’s owner settled claims before trial, underscoring how high the stakes were for tech firms.
Former insiders have warned for years about features that keep users engaged; companies maintain their safety measures are robust but the jury found them insufficient.
Attention is turning to the legal protections that currently shield platforms, notably Section 230 in the United States.
Lawmakers have already been debating reforms, and this verdict is likely to intensify political and regulatory scrutiny.
One potential outcome is curbing or removing features that maximise time on site — endless scrolling, algorithmic recommendations and autoplay — but that would hit the ad-driven business model at the heart of major platforms.
The ruling also adds momentum to actions taken in other countries.
Australia has already blocked under-16s from leading social networks, and policymakers in the UK and elsewhere are weighing similar limits for minors.
In Britain, parliamentarians are still negotiating an amendment to the Children’s Schools and Wellbeing Bill that would give ministers a year to decide which services should be off-limits to under-16s.
Campaigners, including parents who have lost children to harmful online challenges, say the verdict strengthens the case for urgent reform.
This decision is not final — appeals are expected — but it marks a clear turning point.
Whether through courts, regulators or legislation, the pressure is on platforms to rethink designs that prioritise engagement over young users’ wellbeing.
