UK Online Safety Act Categorisation

Category 1 applies where a regulated user-to-user service exceeds 34 million average monthly active UK users and uses a content recommender system, or exceeds 7 million average monthly active UK users and has both a content recommender system and functionality for users to forward or share regulated user-generated content with other users.

Category 2A applies where a regulated search service, or the search engine of a combined service, exceeds 7 million average monthly active UK users and is not the specified type of vertical search engine limited to selected sites or databases under a relevant arrangement.

Category 2B applies where a regulated user-to-user service exceeds 3 million average monthly active UK users and provides qualifying direct messaging designed so messages cannot be encountered by other users unless the sender or recipient takes further action.

For each relevant service part, calculate the mean of its monthly active UK user numbers over the six-month period ending in the month before Ofcom's assessment begins. If the service has operated for less than six months, use its period of operation. An active UK user is one who accessed the user-to-user part or, for search, encountered search content in or via results. Retain the monthly figures, service boundary, period, and calculation; global accounts or registrations are not substitutes.

An internal threshold calculation is a monitoring decision, not the formal categorisation result. Ofcom assesses services, gives affected providers an opportunity to make representations, and publishes the register required by section 95. Check the current register entry for the service and part being assessed.

A service can appear in more than one category, and only the relevant part may be categorised. Ofcom's register, for example, explains that category treatment of a search function within a combined service does not automatically extend to non-search chatbot or feed functionality.

All three categories are subject to transparency reporting after an Ofcom notice. Category 1 services also face additional user-empowerment, content, terms, and fraudulent-advertising duties; Category 2A services have additional search and fraudulent-advertising duties; Category 2B services have additional transparency obligations. The exact commencement and applicable notice must be checked for each duty.

Category 1 and Category 2A providers must also publish specified risk-assessment findings and provide Ofcom with assessment records as required. Categorisation does not replace the baseline illegal-content, children's access, child-safety, complaints, record-keeping, or enforcement duties.