Discord is testing face scanning to verify some users' ages in the UK and Australia.
The social platform, which says it has over 200 million monthly users around the world, was initially used by gamers but now has communities on a wide range of topics including pornography.
The UK's online safety laws mean platforms with adult content will need to have "robust" age verification in place by July.
And social media expert Matt Navarra told the BBC "this isn't a one-off – it's the start of a bigger shift".
"Regulators want real proof, and facial recognition might be the fastest route there," he said.
But campaigners have said these types of checks are ineffective and could lead to privacy issues.
"Age assurance is becoming the new seatbelt for the internet," said Mr Navarra.
"Will it become the norm in the UK? Honestly, yes, probably."
He said he believed the incoming changes in online safety laws mean online platforms would beef up their age verification processes.
"The era of 'click here to confirm you're 13' is dead," he said.
"Get age verification wrong now, and you don't just lose users – you could lose a courtroom battle or incur fines."
Firms which do not comply with the Online Safety Act could be fined up to 10% of their global turnover.
Instagram previously brought in age checks using facial analysis in 2022 for users who want to change their profile settings to be over 18.
The social media company requires users to take a selfie video on their phone and uses AI to estimate the person's age.
Like Discord, they can alternatively upload a picture of their photo ID.
