A landmark trial began in Oakland, California, in which lawyers for 29 US states, including California and New York, accuse Meta of deliberately designing Facebook and Instagram to be addictive to children and failing to keep users under 13 off its platforms. The case, described as the biggest legal challenge Meta has faced, will run for six weeks before a jury and could force major changes to the platforms as well as substantial financial penalties, making it a significant test of tech companies' responsibility for young users' wellbeing.

In opening arguments, a lawyer for California claimed Meta identified "millions" of 11 and 12-year-olds on Instagram and did little to remove them, citing internal research showing "1 in 5 teens says Instagram makes them feel worse" and that features boosting time spent conflict with users' wellbeing. Meta's lawyer countered that only around 100,000 underage users were found, argued that privacy laws prevent the company from verifying ages more precisely, and disputed that social media addiction exists at all, pointing to statements from Mark Zuckerberg and Instagram head Adam Mosseri and to figures showing 41% of teens said Instagram made them feel better.