Aylo, the owner of adult sites Pornhub, YouPorn and RedTube, says it will introduce "government approved age assurance methods" in the UK.
The company has not yet revealed how it will require users to prove they are over 18, but UK regulator Ofcom says simply clicking a button, which is all the adult site currently requires, is not enough.
Pornhub has resisted age checks elsewhere, including in France - where it recently suspended its site amid a battle over the country's age verification rules.
Under the Online Safety Act pornographic sites must introduce "robust" age checking techniques, such as demanding photo ID or running credit card checks for UK users, by this summer.
Aylo said it would introduce the new methods to check user ages on its sites by 25 July.
