Ofcom has set out its recommendations on how to identify which of the United Kingdom's millions of social media users are aged over 16.
Under the ban, due to come into force in March next year, those under that age will be prevented from accessing ten of the biggest platforms, including Instagram, TikTok and Snapchat.
In addition to traditional forms of identification, the regulator recommended four methods it says would be "highly effective" at gauging people's ages: photo ID matching, in which information on a document such as a passport is checked against a live image taken during the check; banking-based checks, using the information a financial institution holds on a user's age; face age estimation technology, which the regulator argues has recently improved; and digital ID services.
The recommendations are subject to government approval. Ofcom's report will now be considered by ministers, with a decision due by the end of the year.
Age verification below 18 is difficult, the regulator notes, because 16 and 17-year-olds do not have credit cards or full driving licences and may not have passports either, and because they can look significantly older or younger than they are.
How to comply will be left to the platforms. "What we've learned in introducing age checks across the porn industry is that actually what a lot of countries did before us was say you need to do it this way and they were very prescriptive and it didn't work," Ofcom's chief executive, Dame Melanie Dawes, told the BBC. "So what we've said all along is here are things that can work, they must preserve privacy, they must protect people's data, but it's on you to put in place what you think works for you."
Some companies, Meta among them, have called for checks to be applied at device level, so that an under-age user would be blocked from installing the apps through an app store at all. Meta said this would reduce the burden of repeated verification across multiple platforms, and told the BBC that it already applies some of the recommended methods. Ofcom says device-level checks would not absolve platforms of running their own.
A similar ban was introduced in Australia last year, and many children there found ways around it. Child safety campaigners, including the NSPCC and the Molly Rose Foundation, welcomed Ofcom's guidance while pointing to lessons from the Australian rollout. The regulator acknowledges that "the risk of circumvention cannot be entirely eliminated".
Ofcom said it did not have a firm number for how many adults would need to prove that they are not under age, but conceded that it would be a "large number of accounts" that the platforms would need to "deal with".
That last paragraph is the one worth keeping. The ban applies to people under 16. The checks apply to everybody, because the only way to find the people the rule is about is to ask the people it is not about.
The United Kingdom has about as many adults as it had last week, and every one of them with an account is now to establish a fact that is of no interest to anyone unless it turns out to be false. This newspaper has searched for a precedent and can offer only the smoke alarm, which also sounds in every room in order to locate the one that is on fire.
The four recommended methods illustrate the difficulty from the other side. A passport check confirms that the holder is old enough to hold a passport. A banking check confirms the age a bank wrote down. Face age estimation produces an estimate, which is the word for a number that is not the age. Digital identity confirms an identity, which was never the part in dispute.
Our analysts are drawn instead to the group the regulator has itself identified as the hard case: 16 and 17-year-olds, too old for the ban, too young for the documents, and capable of looking either. They are the only people whose age cannot be settled by any of the four methods, and also the only people whose age the rule turns on.
The Department of Unnecessary Research accepts the regulator's position that the risk of circumvention cannot be entirely eliminated, and adds one observation drawn from the same report. The checks will work best on the people who have nothing to prove.