Social media is on trial in Los Angeles. What happens next could change the way they operate.
Inside LA's superior court, a landmark trial is getting under way. Social media companies are being accused of being addictive by design, a bit like tobacco and cigarettes were in the 1980s.
They'll face around 22 "bellwether" lawsuits, i.e. test cases, with lawyers considering the testimonies of more than 1,500 people when launching the action.
Opening statements for the first lawsuit will start on Monday, with Meta chief executive Mark Zuckerberg among the tech execs expected to testify.
Over the years, people have tried to sue the owners of Instagram, Facebook, YouTube, TikTok and Snapchat for online harm, but they've largely failed.
Often, social media companies will rely on a defence called Section 230 of America's Communications Act, which protects online platforms publishing third-party content.
It says they're not responsible for content posted by users on their platforms.
So what makes this court case so different?
For the first time, social media companies will face a trial by jury.
Those jurors won't decide whether specific content on the platforms was harmful. Instead, they'll decide whether social media companies were negligent when they created and tweaked their products to encourage people to spend more time on them.
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A feature expected to come up, for example, is "infinite scrolling", whereby your social media feed never ends, no matter how long you spend watching it.
The plaintiffs allege that Instagram, Facebook, YouTube, TikTok and Snapchat "have rewired how our kids think, feel, and behave", according to the class action master complaint.
If the jurors decide the companies were negligent when creating their products, they'll then also need to decide whether that negligence led to the significant harm of a young person.
In this case, that person is known as KGM, a Californian 19-year-old who says she suffered anxiety, depression and body image issues after using Instagram, Snapchat, TikTok and YouTube as a child.
TikTok and Snapchat have already settled out of court with her, leaving just Meta and YouTube on trial.
This is a "bellwether" trial, meaning it is being used as a test case to see how much compensation victims could be due in future litigation against social media companies.
If the tech companies lose, they could be forced to change the designs of their platforms.
Although TikTok and Snapchat settled for this case, they'll be involved in the future cases.
The head of Instagram, Adam Mosseri, will also testify during the trial.
The tech companies say there's no clear link between tech use and addiction, and that there needs to be strong proof that they significantly harmed young users.
In a blog post, Meta said this kind of legal action against them "oversimplifies" the "complex issue" of teenage mental health.
"Narrowing the challenges faced by teens to a single factor ignores the scientific research and the many stressors impacting young people today, like academic pressure, school safety, socio-economic challenges, and substance abuse," said the post.
In a statement to Sky News, Google also rebuffed the claims.
"Providing young people with a safer, healthier experience has always been core to our work," said Google spokesperson Jose Castaneda.
"In collaboration with youth, mental health and parenting experts, we built services and policies to provide young people with age-appropriate experiences, and parents with robust controls.
"The allegations in these complaints are simply not true."
(c) Sky News 2026: Social media goes on trial in LA - here's what you need to know

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