Brazil’s Supreme Federal Tribunal (STF) has finalised a binding legal thesis that fundamentally reshapes the liability of social media platforms for third-party content, marking the culmination of a year-long judicial process. The ruling, delivered on Wednesday after the court resolved outstanding clarification motions from companies including Meta and Google, establishes that platforms can be held solidarily liable for damages arising from illegal posts by users. However, it carves out an exception: liability is waived if the provider demonstrates it conducted a “diligent analysis” and faced “reasonable doubt” about the content’s illegality. The thesis imposes a proactive “duty of care,” requiring platforms to create mechanisms to curb unlawful material and to offer efficient channels for user reports and removal requests. Certain categories—child sexual abuse material, terrorism, racism, incitement to violence and suicide, and hate speech against women—must be taken down immediately upon extrajudicial notification, without waiting for a court order. The court gave companies 60 days to adapt their systems, and the thesis now serves as a mandatory guideline for all Brazilian courts, effectively overriding the previous framework under Article 19 of the Marco Civil da Internet.

The Brazilian decision arrives amid a broader global push to hold technology firms accountable for harms amplified by their algorithms. Viewed from Washington, the state of New Mexico is pursuing nearly $1 billion in penalties from Meta after a jury found the company liable for endangering children and misleading the public about platform safety. In Europe, an Italian mother has filed suit against Meta and TikTok over the suicide of her 12-year-old daughter, alleging that the platforms’ recommendation systems relentlessly fed the girl self-harm content, creating a secret online identity that her parents discovered only after her death. These cases underscore a growing international consensus that the era of blanket platform immunity is receding, though the precise legal mechanisms differ sharply across jurisdictions.

Within Brazil, the regulatory picture is further complicated by a decree issued by President Luiz Inácio Lula da Silva that, according to legal scholars in Rio de Janeiro, goes beyond the STF’s ruling. Professor Carlos Affonso Souza of the State University of Rio de Janeiro argues that the executive measure introduces additional obligations not contemplated by the court, injecting fresh uncertainty into an already fluid landscape. While the STF’s thesis provides a constitutional floor, the decree signals the government’s appetite for stricter controls, potentially setting up tensions between judicial and executive approaches to platform governance.

The 60-day implementation window will test whether platforms can operationalise the duty of care without resorting to excessive automated filtering that might suppress legitimate speech. The “reasonable doubt” defence is likely to become a central battleground in future litigation, as courts grapple with what constitutes diligent analysis in the face of algorithmic scale. Analysts in London note that Brazil’s model—combining extrajudicial takedown obligations with a carve-out for good-faith uncertainty—could influence regulatory debates in other middle-income democracies wrestling with similar dilemmas. Yet the interplay with Lula’s decree and the potential for further legal challenges mean the final architecture of platform accountability in Brazil remains a work in progress, mirroring the fragmented global response to the power of big tech.