A California state court on Monday began hearing a case that will test whether social media companies can be held liable for harm caused by allegedly addictive app design, as a young woman claims Instagram and YouTube contributed to her mental health struggles during adolescence.
Opening statements were delivered in Los Angeles in a lawsuit brought by a 20-year-old California resident identified in court filings as K.G.M. She is suing Meta Platforms, the parent of Facebook and Instagram, and Alphabet, which owns YouTube, seeking unspecified damages. The plaintiff alleges that features designed to maximise user engagement led to compulsive use of the platforms when she was a minor, worsening depression and suicidal thoughts.
The case is among thousands filed across the United States accusing major technology companies of harming young users through product design. Legal experts say a verdict in favour of the plaintiff could have implications beyond California, potentially weakening a long-standing legal shield that has helped protect internet companies from liability tied to user harm.
According to court documents, K.G.M.’s lawyers plan to argue that Meta and Google were negligent in designing their platforms, failed to adequately warn users and parents about mental health risks, and played a substantial role in causing her injuries. If the jury agrees, it will be asked to consider damages for pain and suffering and may also weigh punitive damages.
The defendants are expected to challenge those claims by pointing to other factors in the plaintiff’s life, highlighting safety measures introduced for young users, and arguing that responsibility for harmful material lies with those who post content rather than with platform design. Under US law, internet companies generally benefit from broad protections that limit their liability for user-generated content.
The trial is expected to run into March. Mark Zuckerberg is expected to testify for the defence. Two other companies originally named in the case, TikTok and Snap, reached settlements with the plaintiff before the trial began, according to court records.
Meta and Google are among several technology companies facing extensive litigation in California state courts over similar allegations. Along with TikTok and Snap, they are defendants in thousands of lawsuits claiming that social media platforms are addictive by design and contribute to mental health problems among children and teenagers.
In parallel to the state cases, more than 2,300 related lawsuits have been consolidated in federal court. Those actions have been brought by parents, school districts and state attorneys general. The federal judge overseeing the cases is currently considering whether the companies’ liability protections apply, ahead of a first federal trial that could take place as early as June.
A separate case also began on Monday in Santa Fe, New Mexico, where the state attorney general has accused Meta of exposing children and teenagers to sexual exploitation on its platforms and profiting from such activity. Meta has denied those allegations.
The litigation reflects a broader international push to scrutinise the impact of social media on children’s wellbeing. Several governments have introduced or proposed age-based restrictions on access to platforms. Australia and Spain have already barred children under 16 from using certain social media services, while other countries are weighing similar measures.
The Los Angeles case is being closely watched by regulators, parents and the technology industry, as it could influence how courts assess claims that digital platforms are harmful not because of individual content, but because of the way they are designed.