For the first time, a massive group of parents, teens and school districts is taking on the world’s most powerful social media companies in open court, accusing the tech giants of intentionally designing their products to be addictive. The blockbuster legal proceedings may see multiple CEOs, including Meta’s Mark Zuckerberg, face harsh questioning.

A long-awaited series of trials kicks off in Los Angeles superior court on Tuesday, in which hundreds of US families will allege that Meta, Snap, TikTok and YouTube’s platforms harm children. Once young people are hooked, the plaintiffs allege, they fall prey to depression, eating disorders, self-harm and other mental health issues. Approximately 1,600 plaintiffs are included in the proceedings, involving more than 350 families and 250 school districts.

“The fact that a social media company is going to have to stand trial before a jury … is unprecedented,” Matthew Bergman, founder of the Social Media Victims Law Center and an attorney representing plaintiffs, said in a press briefing.

The initial trial is expected to last six to eight weeks. It involves a 19-year-old who is identified in court documents by the initials KGM. She alleges that she developed mental health issues at a young age after becoming addicted to social media apps.

Her case will be the first of around 22 “bellwether” trials, which are used as test cases to gauge juries’ reactions and potential verdicts. Ultimately, the landmark trials will cover thousands of lawsuits that have been coordinated together in what is known as a judicial council coordination proceeding (JCCP).

The plaintiffs in these cases are seeking financial damages and injunctive relief that would change the design of the platforms and establish industry-wide safety standards. If they win and prove that millions of children have been harmed by social media, it could profoundly change how these platforms are designed and create new avenues for lawsuits against the tech behemoths.

Key witnesses are expected to include top executives from the social media companies, such as Snap CEO Evan Spiegel, Instagram’s Adam Mosseri and Zuckerberg, along with experts in online harm.

Meta and Snap did not respond to requests for comment. TikTok declined to comment.

YouTube spokesperson José Castañeda called the allegations in the lawsuits “simply not true”. He said providing young people with a “safer, healthier experience has always been core to our work” and that “we built services and policies to provide young people with age-appropriate experiences, and parents with robust controls”.

Troves of unsealed documents and untold harms could be revealed

Just a week before KGM’s trial was set to begin, Snap reached a settlement agreement with her lawyers in which the company denied wrongdoing. Financial terms of the settlement were not made public. Snap is still a defendant in other suits in the state-level trial, and Meta, TikTok and YouTube have made no settlement agreements in the case.

Snap said in a statement at the time that the company was “pleased to have been able to resolve this matter in an amicable manner”.

Sacha Haworth, the executive director of the Tech Oversight Project, which has been involved in advocacy work for the plaintiffs, said: “You don’t settle unless you don’t want that stuff to be public … The public doesn’t really know what is coming.”

Lawyers for the plaintiffs are using a similar playbook to what was used against tobacco companies in the 1990s, which focused on cigarettes being addictive and companies publicly denying that for decades while knowing of their products’ harms. The legal team working on the social media cases say that troves of internal company documents will be unsealed during trial and the public will hear testimony from children and parents that has never before been revealed. The details of KGM’s case have been under seal but are slated to be made public during trial.

Julia Duncan, an attorney with the American Association for Justice who is involved with the case, said some of the unsealed documents will show company employees admitting to the addictive nature of the platforms, because of features such as infinite scroll, video autoplay and the way recommendation algorithms are designed.

For example, Duncan said, one unsealed document shows an Instagram employee calling the app a “drug” and another employee saying, “lol, we’re basically pushers”.

The social media companies have argued that how people use their services is up to each individual. These companies have also long maintained they’re protected under section 230 of the Communications Decency Act, a federal law that exempts platforms from legal liability for content generated by their users.

Bergman, KGM’s lawyer, said the social media companies “operate in the world in a way that no other company does” since they have long been absolved from liability because of section 230. This time is going to be different, he said. The judge in the case ruled in November that jurors must look not only at content on the platforms, but also at the companies’ design choices.

“There is a lost generation of kids,” Bergman said. “This was not an accident, this was not a coincidence … this was a design choice.”

A separate series of federal trials is scheduled to take place in San Francisco in June in what’s called a multi-district litigation (MDL). The allegations in these cases are similar to the state trials and involve more than 235 plaintiffs, including families, school districts and attorneys general from nearly three dozen states.

The slew of lawsuits comes after several company whistleblowers have spoken out publicly, alleging the social media companies knew their products were harming children and did little-to-nothing to halt it. A bipartisan group of US lawmakers have repeatedly grilled company executives in congressional hearings alleging the businesses push content to youth that promotes bullying, drug abuse and self-harm.

At one hearing in January 2024, Republican senator Josh Hawley prodded Zuckerberg into publicly apologizing. Despite Zuckerberg’s apology, the families involved in the trials say Meta executives looked the other way and children continued to be harmed.

“Every parent is struggling with their kids and these platforms. Every parent,” said Juliana Arnold, a founding member of Parents RISE, whose teenage daughter died in 2022 from overdosing on deadly pills after messaging a dealer on Instagram. “We’ve been waiting for this for years – to let the truth come out.”