Australia banned under-16s from social media in a world-first crackdown on Wednesday, declaring it was time to "take back control" from formidable tech giants.
A raft of popular apps and websites -- Facebook, YouTube, Instagram and X among them -- face US$33 million fines if they fail to purge Australia-based users younger than 16.
Australia becomes one of the first nations to push back so forcefully against tech companies with immense political power, in a move other countries are looking at closely.
"Enough is enough," Prime Minister Anthony Albanese said.
"It is one of the biggest social and cultural changes that our nation has faced.
"We will take back control."
The government says unprecedented measures are needed to protect children from "predatory algorithms" filling phone screens with bullying, sex and violence.
The laws came into effect after midnight local time across Australia.
Hundreds of thousands of adolescents woke up to find themselves locked out of apps they once scrolled through for hours each day.
Bianca Navarro, 10, was already counting the years until she could log in again to YouTube.
"It will be pretty sad because I have six years until I can watch it," she told AFP.
- Blacklisted -
Facebook, Instagram, YouTube, TikTok, Snapchat and Reddit are forbidden from creating or keeping accounts belonging to users in Australia under 16.
Streaming platforms Kick and Twitch are also on the government's blacklist, as are Threads and X.
The ban has been hailed as a godsend for parents sick of seeing children stuck to their phones.
Mia Bannister blamed social media for the suicide of her teenage son Ollie, who killed himself last year after he was bullied online.
He was also being served endless dieting videos that fuelled an eating disorder, she said.
"I'm sick of the social media giants shirking responsibility," she told AFP in the lead-up to the ban.
"The problem is we hand them a phone and we hand them the greatest weapon we could hand them."
A growing body of research suggests too much time online is taking a toll on teen wellbeing.
But it is hard to draw firm conclusions that separate phone use from other lifestyle factors, experts say.
Father-of-five Dany Elachi said the restrictions were a long-overdue "line in the sand".
"We need to err on the side of caution before putting anything addictive in the hands of children," he told AFP.
- 'Really distracted' -
Tech-savvy teenagers the world over have taken an interest in Australia's measures.
"Students nowadays, they are really distracted," said Nigerian high-schooler Mitchelle Okinedo, 15.
"Social media today is very important for expressing yourself, no matter how old you are," said Santiago Ramirez Rojas, 16, from Mexico City.
YouTube, Meta and other social media giants have lined up to condemn the ban.
Meta, the parent company of Facebook and Instagram, said children were already flocking to darker online spaces.
"We've consistently raised concerns that this poorly developed law could push teens to less regulated platforms or apps," the US-based firm told AFP in a statement.
"We're now seeing those concerns become reality."
Elon Musk's X told young users the ban was "not our choice".
"It's what the Australian law requires."
Lesser-known chat and image-sharing apps Lemon8 and yope, which are not currently listed in the social media ban, have shot up the download charts in Australia.
While most platforms have begrudgingly agreed to comply, for now, legal challenges are in the wind.
Online discussion site Reddit said Tuesday it could not confirm local media reports that said it would seek to overturn the ban in Australia's High Court.
An Australian internet rights group has launched its own bid to have teenagers re-instated to social media.
- Rushed or reasonable? -
Australia's efforts will be closely watched by all those worried about the dangers of social media.
New Zealand and Malaysia are mulling similar restrictions.
The Australian government concedes the ban will be far from perfect at the outset and canny teenagers will find ways to slip through the cracks.
But platforms face the threat of Aus$49.5 million (US$33 million) fines if they fail to take "reasonable steps" to stop this happening.
It remains to be seen how Australia's internet safety regulator will interpret what counts as reasonable.
Social media companies bear the sole responsibility for checking users are 16 or older.
Some platforms say they will use AI tools to estimate ages based on photos, while young users may also choose to prove their age by uploading government ID.
Which platforms fall under the ban continues to be debated.
Popular apps and websites such as Roblox, Pinterest and WhatsApp are currently exempt -- but the government has stressed that the list remains under review.
Most social media platforms already require users be at least 13, a legacy of US laws setting the minimum age for data collection without parental consent.
