European regulators have put Meta on notice over the way Facebook and Instagram are built to keep people hooked.

In preliminary findings issued Friday, the European Commission said Meta's use of "addictive design" puts the company in breach of the EU's Digital Services Act (DSA), the bloc's flagship online safety law. According to CNBC, the finding covers design features on both Instagram and Facebook.

The BBC reports that regulators singled out features such as infinite scroll, which they say contribute to "compulsive use" and "unhealthy habits." Engadget notes the Commission's position is that these designs are effectively illegal under the DSA.

The findings are not final, but the message is pointed. According to Adam Satariano of the New York Times, reported via Techmeme, the Commission told Meta to make changes or risk a hefty fine. The Verge reports that Meta is likely to be forced to redesign both apps, and could face a penalty of up to $12 billion. The Verge also quotes the Commission saying Meta "did not adequately" address the concerns, though the full statement was not provided in the source.

A preliminary finding is a step in the process, not a verdict: Meta typically has an opportunity to respond and adjust before any penalty is confirmed.

Why it matters: this is one of the most direct regulatory challenges yet to the engagement-driven design that powers social media, and if it holds, it could force Meta to rebuild how two of the world's most-used apps work — with consequences for how the whole industry treats features meant to keep users scrolling.