2024 witnessed the highest levels of online child sexual abuse material ever observed since records began, with the Internet Watch Foundation (IWF) identifying 291,273 webpages containing child sexual abuse imagery, links to imagery, or the advertising of this (IWF, 2025), facilitated through online communities accessible via the surface web (i.e. social media platforms, and online gaming communities). The sheer scale and harms caused by these crimes have led to calls for this to be viewed as a global public health issue, in need of an immediate and coordinated response. However, research into the nature of such online communities is largely limited in scope, with focus predominantly targeting potential perpetrators and their access to online communities (rather than the safeguarding activities of specific online platforms). This chapter seeks to bridge this gap, presenting work exploring the role played by online communities (i.e. through social media and gaming platforms) in preventing online child sexual abuse. Specifically, the chapter examines current practices utilised by such platforms (as well as challenges faced) in the fight against online child sexual abuse. This includes the impact of the ever-growing use of generative AI, as well as the need to hold technology companies to account for content hosted on their platforms, particularly considering the recently implemented Online Safety Act 2023.