Mark Zuckerberg, the Facebook co-founder, arrived at a California court on Wednesday where he is due to testify in a landmark legal case over whether social media is addictive to children.

It will be Zuckerberg's first appearance before a jury after years of backlash against his company, Meta Platforms, which also owns Instagram and WhatsApp.

Lawyers for Meta have argued the lead plaintiff in this case, known by her initials K.G.M, was hurt by other things in her life and not by her use of Instagram.

The Los Angeles trial, in which Google's YouTube is also a defendant, is being closely watched for its implications for thousands of similar lawsuits facing social media giants.

TikTok and Snapchat, which had also been named in the lawsuit, settled shortly before trial was scheduled to begin. Terms of the settlements were not disclosed.

Lawyers for K.G.M., who started using Instagram and YouTube as a child, have accused social media firms of working to addict young users, despite being aware of risks to mental health.

Zuckerberg, who arrived at court with an entourage of security and associates, is expected to face questions about Instagram's design and what changes the firm made over the years in order to keep people hooked.

Meta's advertising-based business model, which depends on metrics such as how long people stay on the platforms, is also likely to be in focus.

Bereaved parents were among those in the courtroom to watch the proceedings.

In questioning last week, Adam Mosseri, the head of Instagram, challenged the idea of social media addiction, arguing that even 16-hours of Instagram use in a single day did not show an addiction.

The trial is expected to last several weeks. It is also set to include testimony from former Meta employees who have since spoken out about on the company's practices.

YouTube boss Neal Mohan had also been expected to appear but is no longer being called for testimony, the BBC has learned.

The case is one of thousands of similar lawsuits brought by families, state prosecutors and school districts currently winding their way through US courts.

The lawsuits accuse Meta and other social media platforms, including TikTok, Snapchat and Youtube, of functioning in an addictive manner that ultimately has harmed many children.

In one such case, 29 state attorney generals are pushing a California federal court to demand that the platforms make a number of changes immediately, before any trial, including forcing Meta to remove all accounts known to belong to users under 13 years of age.

A growing number of countries are moving to restrict social media use by young people. Australia late last year implemented a ban on social media accounts for people under age 16.

The UK, Denmark, France and Spain are considering similar measures.