Google's YouTube shared a "disappointing update" to millions of Australian users and content creators on Wednesday, saying it will comply with a world-first teen social media ban by locking out users aged under 16 from their accounts within days.

The decision ends a stand-off between the internet giant and the Australian government which initially exempted YouTube from the age restriction, citing its use for educational purposes. Google had said it was getting legal advice about how to respond to being included.

"Viewers must now be 16 or older to sign into YouTube," the company said in a statement.

"This is a disappointing update to share. This law will not fulfill its promise to make kids safer online and will, in fact, make Australian kids less safe on YouTube."

The Australian ban is being closely watched by other jurisdictions considering similar age-based measures, setting up a potential global precedent for how the mostly US tech giants behind the biggest platforms balance child safety with access to digital services.

The Australian government says the measure responds to mounting evidence that platforms are failing to do enough to protect children from harmful content.

Signed out

YouTube said any user aged under 16 would be automatically signed out of their account from December 10, meaning they could no longer subscribe, like or comment on posts although they could still view content logged out.

That meant underage content creators also could not log in or post. YouTube did not say how it would verify someone's age.

The company also reiterated its position that the ban would not make the internet safer, and said in an email to caregivers of underage users that "parental controls only work when your pre-teen or teen is signed in, so the settings you've chosen will no longer apply".

Communications Minister Anika Wells, speaking to reporters in Canberra, said it was "weird that YouTube is always at pains to remind us all how unsafe their platform is in a logged out state".

"If YouTube is reminding us all that it is not safe and there's content not appropriate for age-restricted users on their website, that's a problem that YouTube needs to fix."

The law prohibits platforms from allowing under-16s to hold accounts, with penalties of up to A$49.5 million ($32.5 million) for breaches. Meta's Facebook and Instagram, TikTok and Snap's Snapchat previously said they would comply.

Of the platforms named by the government as being covered by the ban, only Elon Musk's X and message board Reddit have not publicly committed to abide by the law.

Wells, asked about reports of lesser-known social media apps growing in popularity, said the tech industry was "dynamic" and the government's list of affected platforms "will need to expand as different platforms receive migratory patterns".

YouTube has 325,000 accounts held by Australians aged 13 to 15, according to regulator the eSafety Commissioner, behind only Snapchat which has 440,000 and Instagram which has 350,000 in that age range.

eSafety has said more than one-third of Australians aged 10 to 15 have reported seeing harmful content on YouTube, the worst of any platform.