The settlements avoid a California trial next month that had been expected to set the tone for hundreds of similar cases.
Meta, which owns Facebook and Instagram, was the last of the four companies to settle, according to court documents filed in federal court in Oakland, near San Francisco.
Snap, TikTok and Google -- which owns YouTube -- had already settled on May 15, according to documents reviewed by AFP.
The deals come as the legal environment for social media platforms grows increasingly hostile.
In March, a Los Angeles jury ordered Meta and YouTube to pay US$6 million to a young woman, ruling that their platforms were harmfully addictive -- a first-of-its-kind verdict.
