Mark Zuckerberg, CEO of Meta Platforms, is expected to testify Wednesday in a landmark social media addiction trial in California, where a plaintiff alleges that Instagram and other platforms were intentionally designed to make young users addicted.
The 41-year-old executive, whose company owns Facebook, Instagram and WhatsApp, is considered the most high-profile witness in the case. The trial is the first in a series of lawsuits brought by American families against major social media companies and could help shape the legal direction of thousands of similar claims.
It will mark the first time Zuckerberg addresses the safety of Meta’s platforms directly before a jury. His influence has loomed over proceedings since jury selection, during which Meta’s legal team sought to exclude California residents they believed were overly hostile toward the tech billionaire.
Jurors in Los Angeles are expected to hear testimony through late March as they consider whether Google-owned YouTube and Meta’s Instagram bear responsibility for mental health issues suffered by Kaley G.M., a 20-year-old California resident who has used social media heavily since childhood.
According to court filings, Kaley began using YouTube at age six, joined Instagram at 11, and later used TikTok and Snapchat.
The central question before the jury is whether Google and Meta deliberately structured their platforms — including algorithms and personalisation features — to encourage compulsive use among young people, potentially harming their mental health.
The case, along with two similar trials scheduled later this year in Los Angeles, seeks to establish a legal benchmark for resolving thousands of lawsuits alleging that social media has contributed to rising rates of depression, anxiety, eating disorders and suicide among young people.
The trial focuses specifically on app design and platform features, as US law generally shields companies from liability related to user-generated content. TikTok and Snapchat, also named in the complaint, reached confidential settlements with the plaintiff before proceedings began.
Earlier this month, Instagram chief Adam Mosseri testified and rejected the label of social media addiction, preferring the term “problematic use.”
“I’m sure I’ve said that I was addicted to a Netflix show when I binged it really late one night, but I don’t think that’s the same thing as clinical addiction,” Mosseri told jurors.
The plaintiff’s legal team also called psychiatrist Anna Lembke, who testified that social media could act as a “gateway drug” for young users by influencing brain development and reinforcing addictive behaviours.
Mosseri was also questioned about internal emails concerning cosmetic surgery filters on Instagram. He defended Zuckerberg’s 2020 decision to retain the filters despite objections from some executives who warned they could negatively affect young girls’ self-image. Company officials were reportedly concerned about losing market share to competitors such as TikTok.
YouTube CEO Neal Mohan had been expected to testify but was later replaced by another company executive, according to the plaintiff’s lawyers.
The Los Angeles trial is unfolding alongside a separate nationwide case before a federal judge in Oakland, California, which could lead to another trial in 2026.
Separately, Meta is also facing trial in New Mexico, where prosecutors allege the company prioritised profits over protecting minors from sexual predators.
