TikTok on Tuesday agreed to settle a landmark lawsuit in the United States on social media addiction, said the plaintiff's lawyers.  

The social video platform was one of four companies, including Meta, Snap and Alphabet-owned YouTube, facing allegations that their platforms deliberately addict and harm children.

Snap also settled the case last week for an undisclosed sum.

Details of the settlement with TikTok were not disclosed.

Joseph VanZandt, co-lead counsel for the plaintiff, said Tuesday that TikTok remains a defendant in the other personal injury cases. He added that the trial will proceed as scheduled against Meta and YouTube.

What is the case about?

The lawsuit will be the first in a raft of cases that seek to hold social media companies accountable for harming children's mental health

The case involves a 19-year-old from California, identified "KGM."

She has accused the social media companies of deliberately designing their platforms to make them more addictive to children and teenagers.

KGM claims that her use of social media from an early age addicted her to the technology. It also exacerbated her depression and suicidal thoughts, she said.

The lawsuit is viewed as a bellwether whose outcome will likely have far-reaching consequences for both platforms and users, especially as there are hundreds of related lawsuits accusing platforms of youth.

What do the companies say about the allegations?

The tech companies reject the claims that their products deliberately harm children.

The platforms stress they have put in place a number of safeguards over the years and argue that they are not liable for content posted on their sites by third parties.

A Meta spokesperson said in a statement Monday the company strongly disagrees with the allegations outlined in the lawsuit.

The company said  it's "confident the evidence will show our longstanding commitment to supporting young people."

Jose Castaneda, a Google spokesperson, said Monday that the allegations against YouTube are "simply not true."

In a statement, he said "Providing young people with a safer, healthier experience has always been core to our work."

Zuckerberg expected to testify at the trial

Jury selection in the case starts this week in the Los Angeles County Superior Court.

A number of executives, including Meta CEO Mark Zuckerberg, are expected to testify at the trial, which will last six to eight weeks.

It's the first time the companies will argue their case before a jury.

"This was only the first case — there are hundreds of parents and school districts in the social media addiction trials that start today, and sadly, new families every day who are speaking out and bringing Big Tech to court for its deliberately harmful products," Sacha Haworth, executive director of the nonprofit Tech Oversight Project, told the AP news agency.

Edited by: Louis Oelofse