More than one in five children aged 12 to 17 across Africa, Asia, Latin America and Eastern Europe experienced at least one form of sexual abuse or exploitation on online platforms in the year before being surveyed, the UNICEF report estimated.
Around 15 million children in the countries surveyed were exposed to unwanted sexual content, nine million were pressured into sexual conversations or sharing sexual images, and four million had sexual images shared without their consent, the report found.
The number of children subjected to this abuse globally is certain to run into many tens of millions, it said.
The research, which UNICEF described as one of the largest studies of its kind, was based on national representative surveys collected between 2020 and 2025 of around 21,000 internet-using children in the 21 countries, which included Kenya, Pakistan, Brazil and Serbia.
Almost 60 per cent of reported abuse occurred on social media platforms, led by Facebook, WhatsApp, Instagram, Snapchat and TikTok, while 14 per cent took place in online gaming, the report found.
A spokesperson for Meta, which owns Facebook, WhatsApp and Instagram, said the surveys go as far back as 2020, before the company introduced protections UNICEF recommends such as automatically defaulting teens into private accounts and preventing adults from messaging teens they are not connected to.
It added that it defines WhatsApp as a private messaging app and not a social media platform.
"While the report doesn't provide any specific evidence of abuse, we'll continue to fight child exploitation aggressively across our apps and support law enforcement in prosecuting the criminals behind it," the Meta spokesperson said.
Snapchat pointed Reuters to a blog post by Global Head of Platform Safety Jacqueline Beauchere, who said the company was actively combating online sexual extortion through proactive detection, account removals, user reporting tools and safety features designed to protect vulnerable users.
TikTok said it has built a range of safeguards to protect minors, including restricting certain features for younger users, making accounts for under-18s private by default, and using technology to detect potentially predatory behaviour.
The UNICEF report said more than half the cases involved someone the child already knew, including friends, relatives or romantic partners, while 38 per cent of children first encountered the perpetrator online.
Fewer than one per cent of cases involving children were reported to the police, a social worker or a helpline, according to the research.
The report also highlighted growing concerns over artificial intelligence. Across nine countries where data was collected, an estimated 1.1 million children reported having AI-generated sexual images or videos created depicting them.
Children who experienced tech-facilitated sexual exploitation were around four times more likely to report suicidal thoughts or self-harm and reported significantly higher levels of anxiety than their peers, the research said.
"These experiences cause profound emotional and mental distress. Many children suffer in silence, unsure where to turn for help," UNICEF Executive Director Catherine Russell said.
UNICEF urged governments and technology companies to strengthen safety measures on digital platforms, update laws to address evolving forms of abuse including AI-generated content, and improve child protection and reporting systems.
