There is a long way to go before children under 16 in the UK are blocked from the main social media platforms – as Sir Keir Starmer announced on Monday that they will be. He proposed a date of next spring, although whether, and when, a ban comes in may be up to an eventual successor.

But whatever happens next, a crunch moment has arrived sooner than expected. Until recently, it seemed highly unlikely that the government would seek to restrict the tech industry’s access to children in the way it is now doing. Eighteen months ago, ministers sided with Ofcom in a row over the implementation of the Online Safety Act. Groups including 5Rights argued that companies should be made accountable for harm reduction, as well as obliged to follow new rules. For a mixture of economic and political reasons, the government seemed determined to stay on the right side of big tech and Donald Trump. Its approach was timid.

That has now changed. A 48-page statement from the Department for Science, Innovation and Technology makes a broad case about children’s wellbeing that goes beyond warnings about inappropriate content. It points to the amount of time many children spend online instead of doing other things such as sleeping, as well as concerns about bullying, child sexual abuse, livestreams, inappropriate use of AI chatbots and messaging functions that enable “stranger communication”.

More detail on proposals, including increased protections for 16- and 17-year-olds, is expected soon. Ofcom has been tasked with working out what “highly effective age assurance” that also protects privacy should look like. Screen-time guidance for children aged five and over is also on the way. Following the introduction of a similar ban in Australia, and a UK-wide consultation in which just 11% of parents said that the benefits outweighed the risks of social media, ministers have been emboldened to announce an ambition to “reset norms”.

How people feel about this depends to some extent on their attitude to big tech. Age verification is controversial because it could carry implications for adults as well, depending on how it is implemented. Last week, Sir Keir committed to compulsory nudity-detection on all devices if Apple and Google do not come up with a software fix to protect children by September. There are legitimate fears that data protection laws may not be sufficient to protect privacy if users are required to upload documents to prove who they are.

Even among online safety campaigners, there are differences. In her new book Users: How Big Tech Took Control and How to Fight Back, Beeban Kidron argues that measures to protect children from behavioural manipulation could lead to a wider reining in of tech’s outsize influence. But there is scepticism too about the government’s latest actions. Ian Russell set up the Molly Rose Foundation, named for his daughter who took her own life after being deluged with self-harm content in 2017. He believes that regulation should target algorithms directly, rather than limiting children’s access.

But if much remains unclear, this week’s gear shift is still welcome. For too long, tech companies have used their market power to dictate terms. Sir Keir’s move represents a belated recognition that while these businesses have changed the world in ways that many people appreciate, their overarching goal of maximising engagement with their products is not aligned with human flourishing – and too frequently undermines it.