Meta, Google, TikTok and Snap face more than 3,000 lawsuits over claims their platforms were designed to addict young users, and a US appeals court has just given them the green light to move forward.

The 9th Circuit Court of Appeals rejected an appeal by Meta and TikTok seeking to overturn a lower court ruling. The companies argued that Section 230 of the Communications Decency Act should shield them from liability. But the court ruled that Section 230 provides a defense, not immunity.

The cases, filed by states, municipalities, school districts and individuals, accuse the platforms of intentionally designing features that hook children and teens, contributing to depression, anxiety and body-image issues.

The appeals court also rejected Meta's attempt to delay a separate trial brought by 29 state attorneys general. Jury selection is scheduled to begin on August 12.

The states accuse Meta of illegally collecting children's data, designing Facebook and Instagram to keep young users engaged, and misleading users about platform safety. Meta denies the allegations.

California, Colorado, Kentucky and New Jersey are also pursuing claims under state consumer protection laws. Meta said in a July court filing that the states' proposed penalty calculations could total $1.4 trillion if they prevail.

"A sanction of that size has no analog in the history of consumer protection enforcement," Meta said in the filing.

The legal pressure has been mounting. Days earlier, a New Mexico judge ordered Meta to pay $567 million into a teen mental health fund and adopt youth-safety measures.

That followed a March jury verdict ordering Meta to pay $375 million after finding that it had misled consumers about the safety of its platforms.

Also in March, a California jury found Meta and Google negligent over the design of Instagram and YouTube, awarding $6 million to a young woman who said she became addicted as a child.

Meta, Google, TikTok and Snap are also facing thousands of similar cases in state courts, including around 3,300 lawsuits consolidated in California.