Many users of video-sharing sites such as Onlyfans, Twitch and Snapchat would have difficulty reading and understanding the site rules, according to the media regulator.
Ofcom has looked at how easy it is for people to access the terms and conditions set by six platforms.
It found advanced reading skills were needed to understand them.
It also found their complexity and length meant they were unsuitable for children.
Jessica Zucker, online safety policy director at Ofcom, said: “Terms and conditions are fundamental to protecting people, including children, from harm when using social video sites and apps.