Opening statements begin on Tuesday in a major, multistate jury trial in the United States against Meta, which owns Facebook and Instagram, and which is facing a host of regulatory and legal actions in Europe and beyond.

The US trial opening in the state of California, which could reportedly cost Meta $1.4 trillion in damages, alleges that the social media giant designed addictive social media platforms that are harming the mental health of young people and could significantly change the way these platforms operate if successful, experts say.

US state attorneys general who are bringing the case also say they are concerned about how data on younger users is collected without consent from their guardians.

The case highlights several specific features of these platforms which, according to the attorneys general, specifically harm younger children, such as continuous scrolling and algorithm prompts.

With regulatory action ongoing in Europe and beyond, we look at the impact these cases could have on the workings of social media giants.

Twenty-nine US states have grouped to accuse Meta of designing its platforms in ways that “encourage addictive behaviour, fail to verify users’ ages, encourage adolescents to bypass parental controls, and inadequately safeguard against harmful content and/or intentionally amplify harmful and exploitive content”, according to the filings at the Court of Appeal in California, US.

Meta strongly denies the allegations.

The first four of the states which filed a federal lawsuit against Meta in 2023 – California, Kentucky, Colorado and New Jersey – will begin outlining their cases on Tuesday.

Besides damages, the attorneys general bringing the case are also asking the court to order that changes be made to Meta’s platforms to protect young social media users.

Among other measures, they are demanding that Meta implement a process of parental verification for teenage users; change its “dopamine-manipulating” algorithms; remove image filters for users’ personal images; forbid the creation of multiple accounts; and end “disappearing” messages and posts.

Jury selection was completed last week. The trial is expected to run for about seven weeks, but extra time may be needed if there are unforeseen developments.

A verdict is unlikely to be the final word in the case, as Meta is expected to appeal any decision not in its favour.

Meta CEO Mark Zuckerberg is expected to testify in court, together with the head of Instagram. This will be the second time this year that the Facebook founder has testified, after his February 2026 appearance in a Los Angeles court over similar allegations against Meta. Meta lost that multimillion-dollar case, brought by a young woman referred to as KGM, over platform features linked to addiction in younger users, in March.

How important is this lawsuit and what outcome is expected?

Sonia Livingstone, a professor at the London School of Economics and director of the Digital Futures for Children Centre, told Al Jazeera the case is highly significant.

“It seems unlikely Meta would completely transform the business model or completely remake the feed. But they will surely take some steps to reduce the problem,” she said.

Instead, Livingstone added, the tech company may choose to focus more on moderation and tweaking the platform for those aged below 18.

Nonprofit organisation 5Rights Foundation, which focuses on digital safety, said the case against Meta is an essential first step towards making tech safe for children. “Lawsuits like this can change the practices of tech companies, but only if they are backed by clear rules that are consistently and meaningfully enforced, with penalties large enough to impact their bottom line,” it told Al Jazeera.

This is just the latest in a string of lawsuits being faced by Meta in the US.

Earlier this month, a judge in New Mexico ordered Meta to pay $567m and change how its platforms function for young users in the state after ruling that the company was to blame for harming children’s mental health.

The California case could go further, legal experts say. Julia Powles, executive director of the UCLA Institute for Technology, Law and Policy, told CNBC, “California matters more than any other jurisdiction in the US. It’s where they are subject to the greatest legal reach, and it’s a jurisdiction watched around the world.”

Another 14 US states are set to begin a separate trial against Meta in February 2027.

While action against social media giants in the US is mostly taking the form of lawsuits, elsewhere it is regulators who are leading the charge.

European Union

The EU is pursuing several legal and regulatory cases against Meta, covering antitrust rules for artificial intelligence (AI) on WhatsApp, child safety protections and addictive platform features under the Digital Services Act (DSA).

In 2024, EU regulators opened a formal investigation into Meta for potential breaches of online content rules relating to child safety on its Facebook and Instagram platforms.

The European Commission (EC) said it was concerned that the algorithmic systems used by the popular social media platforms to recommend videos and posts could “exploit the weaknesses and inexperience” of children and stimulate “addictive behaviour”.

Last month, the EC published preliminary findings of a two-year investigation into Meta, saying the company was in breach of the DSA. It called on Meta to implement several design changes to curb “compulsive use”.

The EU specifically accused the group of designing Facebook and Instagram to be “addictive”, and warned that it could face hefty fines if it continues to breach the bloc’s rules under the DSA. It also said Meta has failed to adequately assess the risks Instagram and Facebook pose to users’ physical and mental health.

In July, French lawmakers approved a plan to ban social media for children aged below 16 years from September, but the country’s Constitutional Council struck the ban down last week, saying it would impinge on free speech. The government will now form new legislation which will take this into account.

United Kingdom

In June this year, the UK government announced a sweeping ban on social media for those below 16 to come into force next year. As well as a ban on sites ‌‌such as TikTok, Snapchat and Instagram, the government said it plans actions against gaming and livestreaming services that allow children to talk to strangers. The regulation required to pass the ban is expected in December, while the UK is also considering overnight curfews and ways to prevent infinite scrolling for those younger than 18.

On Tuesday, Dame Rachel de Souza, the children’s commissioner for England, called on the government to go further and introduce more restrictions for people below 18. Following a review of children’s use of social media, which she has published in a report, she said children in the UK are “becoming intoxicated by extremism” and that safety experts have become concerned about children being drawn into radicalisation and violence online.

De Souza is recommending curfews, advertising bans, limits on scrolling and blocking strangers from contacting children across social media platforms, gaming platforms and AI chatbots.

Australia

In December last year, Australia imposed a social media ban on children aged below 16 in December 2025. But earlier this month, a study by the country’s internet regulator revealed that more than eight in 10 young Australian teens and preteens were still using social media platforms.

One main issue, which has prompted the Australian government to accuse Meta and other social media giants of failing to uphold the ban, was that age checks do not appear to work.

About half the children who retained their accounts said platforms had not checked their age, which was the most common reason they were able to stay on the services. Others said their accounts listed them as aged 16 or older, or ‌‌that age-checking ⁠⁠systems had incorrectly determined they were eligible.

Before the ban, nearly 86 percent of children surveyed reported using at least one age-restricted platform. Three months later, that figure remained above 81 percent, a report by the independent online safety regulator eSafety found.

Brazil

A prominent consumer rights organisation in Brazil, the Collective Defence Institute, filed twin lawsuits for 3 billion reis ($525m) in damages against the Brazilian subsidiaries of Meta, TikTok and Kwai in October 2024.

Similar to other complaints, the lawsuits accuse the groups of failing to implement safeguards against addiction and use by children and adolescents.

The key allegations in these lawsuits are that the platforms’ algorithms encourage “compulsive loop-scrolling” by users below 18 years; that there are no effective mental health warnings; that age verification measures are ineffective; and that data protection is poor.

Regulatory measures have also been implemented in Brazil. Since March this year, platforms have been required to link the accounts of children below 16 to legal guardians under the Digital Statute of Children and Adolescents.

In June last year, the Brazilian Supreme Court ruled that tech giants can be held responsible for illegal content posted by third parties on their platforms if they do not remove it quickly enough.

This month, Brazilian regulatory authorities suspended the “Go Live” livestreaming and video-sharing features of Discord across the country. The action followed an investigation into the death of a 13-year-old girl who had allegedly been coerced into self-harm and suicide during a live broadcast, according to news reports.

Kenya

In April 2025, Kenya’s High Court ruled that it has jurisdiction to hear a landmark $2.4bn lawsuit against Meta as the company employs local content moderation contractors in Nairobi and so is subject to Kenyan law. Following the ruling, the case was referred to Kenya’s chief justice to oversee a full constitutional trial.

The case, which claims that Facebook’s algorithms amplified hateful, violent and inciting content which fuelled ethnic violence during the Ethiopia war from 2020 to 2022, has been lodged by Ethiopian researchers Abrham Meareg and Fisseha Tekle, alongside the Kenyan human rights organisation Katiba Institute. They want the court to order Meta to change its algorithms, invest heavily in African content moderation, and establish a $2.4bn restitution fund for victims of the violence.

It is unclear when that case will begin.

Meta is also facing other civil lawsuits in Kenya. In 2023, a Kenyan court ruled it had jurisdiction to hear a case lodged by former workers at a Meta moderation hub, alleging exploitative working conditions and unlawful termination following unionisation attempts.

Rather than completely curtailing the power that social media platforms wield, it is likely that legal action will force them to reform certain features and implement more rigorous age checks, experts say. This could significantly alter the look and feel of social media platforms, they say.

Livingstone said unless platforms start adjusting their design, public tolerance will reach its limits and more restrictive bans against social media platforms might be enforced, however.

She predicted that this might mean the market could diversify more. “It’s not about giving up social media, but opening up to platforms which are less premised on personalised algorithmic feeds, which is addictive and harmful.”