https://www.legislation.gov.uk/ukpga/2023/50/section/12
What's even "harmful content to minors"? Even if it were restricted only to pornography--which is not--I wouldn't count with being able to "moderate" all the ways users can draw penises.
The act regulates "user-to-user" services:
https://www.legislation.gov.uk/ukpga/2023/50/section/3
> In this Act “user-to-user service” means an internet service by means of which content that is generated directly on the service by a user of the service, or uploaded to or shared on the service by a user of the service, may be encountered by another user, or other users, of the service.
The legal text is dense but there is some analysis here:
https://www.eff.org/deeplinks/2023/09/uk-online-safety-bill-...
And some news about Reddit: https://www.eff.org/deeplinks/2025/08/americans-be-warned-le...