UK Online Safety Act: Ofcom publishes final illegal harms codes

Ofcom has published its final illegal harms codes of practice under the Online Safety Act, requiring platforms to implement systems that prevent users from encountering priority illegal content including child sexual exploitation and abuse material. The codes, which take effect in March 2025, mandate proactive technology to detect and remove CSAM, with the largest platforms required to use content classification technology and behavioural signals to identify accounts sharing illegal material, and smaller services obliged to deploy measures proportionate to their risk and capacity.

Mandating detection technology for child sexual abuse material represents a structural shift from reactive reporting to real-time interdiction, a principle Guardii extends across the full spectrum of contact-based harms. Where the UK framework obligates platforms to identify and remove CSAM after upload, anti-grooming and anti-sextortion filters intercept coercive conversations as they escalate, surfacing a child under pressure to a parent or safeguarding professional before imagery is created or transmitted, and routing evidence of an imminent offence to the appropriate authority without exposing staff or moderators to the content itself.