On both sides of the Atlantic, social media has come under mounting scrutiny.
In February, TikTok was charged under EU rules over allegedly addictive features, while in August Meta agreed to pay up to $18 billion to settle U.S. addiction claims.
According to data aggregated by website SocialMediaTransparency.org, the four platforms had a combined reach of 33 million monthly users in Portugal in the first half of 2026.
Company responses and allegations
A spokesperson for Alphabet's Google, owner of YouTube, said providing people with "a safer, healthier experience has always been core to our work" and pointed to tools such as "take a break" and bedtime reminders designed to help users manage viewing habits.
"We'll be assessing this case and responding in due course," the spokesperson said.
Meta, owner of Facebook and Instagram, and TikTok owner ByteDance did not immediately respond to Reuters requests for comment.
Filed by law firm Andersen Tax & Legal Iberia with Lisbon's Civil Court between April and May and disclosed only now after the judicial summer break, the legal action seeks to "hold these platforms accountable and force them to provide a safe experience for their users," D3 said.
D3 highlighted features including infinite scrolling, autoplay videos, persistent notifications and highly personalised recommendation systems.
By removing natural breaks in usage, constantly serving personalised content and repeatedly prompting users to return, platforms create behavioural feedback loops akin to techniques long used in the gambling industry, D3 said.
"Platforms do not have to be hyper-addictive," D3 President Ricardo Lafuente said.
"A healthy, productive and educational social media ecosystem is possible, but only if the rules are robust, properly enforced and directed at those who persist in ignoring them," he said.
D3 files collective actions over platform design
Portuguese digital rights group D3 has filed lawsuits against Facebook, Instagram, TikTok and YouTube, accusing them of designing features in their platforms that keep users hooked, it said on Thursday.
The four collective actions, which allow associations to bring cases on behalf of a broader group of consumers, follow on from lawsuits in other countries that have challenged social media's addictive design.
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