The financial stakes are also unusually high. The states could seek as much as $1.4 trillion in damages, although legal experts have said such a large award is unlikely.

The features that could change

The case is not only about money. The states are challenging the way Meta’s products are built and are seeking changes to features that have become part of everyday social media use.

The states are seeking changes to several features, including like counts, infinite scroll, autoplay, disappearing content such as Instagram Stories, push notifications, multiple-account functions and appearance-changing filters. They argue that these features can encourage young users to spend more time on the platforms and increase social comparison.

Court filings say the states argue that these features can make it difficult for young users to stop using the platforms and can encourage social comparison. The states have also raised concerns about parental consent and age verification for younger users.

Meanwhile, Meta has introduced several safety measures for teenagers. The company says it is using age-assurance technology and AI tools to identify users who may be underage and place them in age-appropriate experiences.

Why the ‘like’ button is being questioned

One of the most familiar parts of Facebook and Instagram is also a major part of the legal dispute. Like counts have been used for years to show how much attention a post is receiving. But the states argue that displaying those numbers can encourage young users to compare themselves with others.

Court records cite Meta’s own research into social comparison and its Project Daisy, an experiment that looked at hiding like counts. The litigation alleges that Meta’s researchers found that hiding like counts could reduce negative social comparison among users.

The issue has also appeared in lawsuits brought by young users.

In one case, a young user described creating multiple accounts and using likes as a way to gain approval and feel better about herself. The litigation around Meta has repeatedly pointed to the way engagement features can encourage young users to return to the platforms.

Infinite scrolling and autoplay are also in the case

The states have also challenged the way users move through Facebook and Instagram. Infinite scroll means there is no obvious stopping point. New posts continue to appear as the user moves down the feed.

Autoplay works in a similar way for video. Content begins playing automatically, allowing users to move from one video to another without deliberately choosing each one.

A federal court has previously described the states’ allegations that these features can make it difficult for young users to disengage from the platforms.

The litigation also challenges temporary content. Instagram Stories, for example, disappear after a set period, and the states say this feature can encourage users to keep checking the platform because they do not want to miss content.

Meta has lost a major child-safety case

The California case comes shortly after another significant legal setback for Meta. In New Mexico, a jury found the company liable in March for misleading consumers and endangering children under the state’s Unfair Practices Act. The jury ordered it to pay $375 million in civil penalties.

A second phase of that case then examined whether Meta’s platforms amounted to a public nuisance and what additional measures should be imposed.

That phase resulted in another $567 million against the company, bringing the total financial liability in the New Mexico case to $942 million. The court also ordered measures aimed at improving protections for users under 18. The platform has said it will appeal.

The reforms ordered in New Mexico include stronger age verification, restrictions on some notifications and changes intended to reduce features that encourage excessive use.

What makes the California case different

The latest federal case involves 29 state attorneys general, although only four states – California, Colorado, Kentucky and New Jersey – are taking part in the first trial. The trial is being heard by US District Judge Yvonne Gonzalez Rogers in Oakland.

The case has an unusual jury arrangement. Rogers selected an advisory jury of eight people, whose decision will not be legally binding. The jury will provide guidance to the judge, who will ultimately decide the case.

Opening arguments are scheduled as the trial gets under way, with proceedings expected to last several weeks.

Rogers has already rejected Meta’s attempt to have claims dismissed. In June, she ruled that claims involving alleged deception, unfair practices and violations of the federal Children’s Online Privacy Protection Act could proceed.

What the states say Meta knew

The states’ case relies in part on internal Meta research and documents. Their lawyers argue that the company knew some of its design choices could affect young users negatively but continued using them because keeping people engaged was important to its business.

The court record includes allegations concerning Meta’s research into social comparison, notifications, temporary content, infinite scrolling and other features.

The states also allege that platform collected personal information from children under 13 without providing the required parental notice and consent mechanisms.

A June court order found that Meta had not provided parental notice, obtained parental consent or provided parents with a way to review their children’s data in the circumstances addressed by the claims.

Meta rejects the allegations

The platform has consistently denied that it deliberately built its platforms in ways that could harm young users. The company has argued that it has spent years developing safety tools and protections for teenagers.

A Meta spokesperson said, “We completely disagree with these allegations and believe the evidence will demonstrate our longstanding commitment to supporting young people.”

The company has also continued to introduce new age-assurance measures. In May, it said it was using more technology to identify accounts that appear to belong to teenagers and automatically place them in its Teen Account protections.

The California trial now puts those competing claims before Judge Rogers, with the advisory jury also weighing the evidence presented by both sides.