All UK porn sites will use "highly effective" age checks within the next month to provide greater protection to children, regulator Ofcom has announced.
Major providers including Pornhub, Stripchat and Jerkmate have agreed to the stronger measures, which apply to both dedicated adult sites and social media, search or gaming services, as part of the Online Safety Act (OSA).
Any company that fails to comply with the checks by July 25 could be fined or could be made unavailable in the UK through a court order.
The platforms must also make sure the measures do not compromise the privacy of adults or prevent them from accessing legal content.
Age assurance methods can include credit card checks, open banking or facial age estimation to verify or guess how old someone is.
The regulator said "the way in which these solutions are implemented in practice" will decide whether it is compliant with the OSA.
It comes after new Ofcom research found that 8% of eight to 14-year-olds in the UK had visited an online porn site or app on smartphones, tablets or computers in a month.
Earlier this month, Ofcom said it had launched a string of investigations into 4chan, a porn site operator and several file-sharing platforms over suspected failures to protect children, after it received complaints about illegal activity and potential sharing of child abuse images.
It said none of the services responded to its legal information requests.
'Harmful'
Oliver Griffiths, Ofcom group director of online safety, said: "Society has long protected youngsters from products that aren't suitable for them, from alcohol to smoking or gambling.
"But for too long children have been only a click away from harmful pornography online.
"Now, change is happening.
"These age checks will bring pornography into line with how we treat adult services in the real world, without compromising access and privacy for over-18s."
A report looking into the use and effectiveness of age assurance methods will be published by Ofcom next year.
