Meta CEO Mark Zuckerberg took the witness stand Wednesday in a closely watched trial examining whether social media platforms intentionally harmed children by designing addictive features. The testimony unfolded in front of a jury — and in the presence of the young woman at the center of the case — as families who say their children were harmed or died because of social media gathered outside the courthouse.
The lawsuit, filed by a California woman identified as “Kaley,” accuses Meta and YouTube of deliberately creating platforms that hooked her at a young age and contributed to serious mental health struggles. The case is seen as a potential test run for hundreds of similar lawsuits nationwide and could expose tech companies to billions of dollars in damages if they lose.
Zuckerberg, appearing before a jury for the first time on allegations related to children’s mental health, told jurors he believed Meta had handled youth safety “in a reasonable way.” Outside the courtroom, however, parents painted a starkly different picture — describing a company they say put profits ahead of children’s wellbeing.
A courtroom filled with parents — and the plaintiff
Zuckerberg arrived at Los Angeles Superior Court shortly after 8:30 a.m., walking past parents, reporters, and jurors waiting to enter. He did not respond when asked what he would say to families who believe social media harmed their children.
Kaley was seated inside the packed courtroom to listen to Zuckerberg’s testimony. Her attorney, Mark Lanier, previously said she would limit her time in court due to social anxiety and difficulty being in large crowds, though she is expected to testify later in the proceedings.
Before testimony began, several parents gathered outside the courthouse holding hands, saying their children had been seriously injured — or died — as a result of social media use.
One of them, Julianna Arnold, told reporters it felt “surreal” to finally see Zuckerberg testify after years of demanding stronger protections for kids. Arnold says her 17-year-old daughter Coco’s death was linked to Instagram use.
“The intention of the company was to prey on teens and exploit them so they could make greater profits,” Arnold said. “That was intentional, not accidental.”
Zuckerberg left the courthouse through a back exit after more than five hours on the stand.
Addictiveness and internal knowledge
During questioning, Lanier challenged Zuckerberg on his past statements, including his 2024 congressional testimony where he said scientific research had not established a clear link between social media use and worsened mental health among young people.
“We get feedback from a range of stakeholders, including people who study wellbeing,” Zuckerberg told the jury. “I considered all of that information and believe I handled this responsibly.”
Lanier later introduced a dramatic visual: a massive poster held by seven people, covered in hundreds of Instagram photos Kaley had posted, underscoring what he described as compulsive use of the platform.
Age limits under scrutiny
A major focus of the testimony was whether children under 13 were able to access Instagram, which officially prohibits users younger than that age. Zuckerberg testified that children under 13 are “not allowed” on the platform.
Lanier countered by presenting an internal Meta document from 2015 estimating that more than 4 million Instagram users were under 13 — representing roughly 30% of U.S. children aged 10 to 12. Kaley, now 20, allegedly began using Instagram at age 9.
At the time, Instagram did not require users to enter a birthdate during signup, instead relying on users to confirm they were at least 13. The company began collecting birthdates from new users in December 2019 and later required existing users to provide that information as part of a youth safety initiative.
Zuckerberg acknowledged that concerns about privacy delayed the change but said the company ultimately made the right decision.
Kaley alleges she sometimes spent several hours per day on Instagram and, on at least one occasion, remained on the platform for more than 16 hours straight. Her lawsuit claims Instagram’s features contributed to anxiety, body dysmorphia, suicidal thoughts, bullying, and sextortion.
Meta has strongly denied the allegations, arguing that Kaley’s mental health struggles stemmed from difficulties at home rather than social media use. YouTube has also rejected the claims.
“The question for the jury is whether Instagram was a substantial factor in the plaintiff’s mental health challenges,” a Meta spokesperson said before Zuckerberg testified.
Time spent vs. “value”
Tensions rose when Lanier questioned whether Meta historically set goals to maximize the amount of time users spent on Instagram. Zuckerberg acknowledged that time-based goals existed in the company’s early years but said Meta later moved away from them.
“There’s a basic assumption that if something provides value, people will use it more,” Zuckerberg said.
Lanier then cited a 2015 internal email in which Zuckerberg outlined a three-year plan that included a goal to increase time spent on Instagram by 10%. Zuckerberg responded that Lanier was mischaracterizing outdated practices and said such metrics were abandoned because they weren’t the best way to run the company.
Zuckerberg maintained that Meta’s goal is to build products people want to use long-term — not platforms that keep users engaged at the cost of their wellbeing.
Filters, free expression, and safety
Lanier also pressed Zuckerberg about Instagram’s decision to allow beauty filters that alter users’ appearances. According to Lanier, Meta consulted 18 experts who found such filters could cause harm.
Zuckerberg testified that Instagram chose not to create or promote those filters itself but allowed users to make them, citing free expression concerns. He said Meta consulted experts on free expression but could not name them and had not personally met with them.
Profits, responsibility, and the jury’s view
Legal analyst Kimberly Pallen told CNN the case may ultimately hinge on whether jurors believe Meta did enough to protect children.
“From the jury’s perspective, it comes down to whether the company cares and whether they acted responsibly,” she said, adding that Zuckerberg’s demeanor on the stand could heavily influence the outcome.
Zuckerberg also discussed his majority ownership of Meta, arguing that strong company performance allows for greater investment in science and research. He noted he has pledged to donate 99% of his wealth.
Lanier then asked whether Zuckerberg would pledge money to victims of social media harms.
“I disagree with the characterization of your question,” Zuckerberg replied.
