All Australians aged under 16 are now officially banned from holding accounts on social media, with 10 platforms so far agreeing to enforce the rules.
Anthony Albanese urged parents and children to have a conversation about the restrictions.
"This is the day when Australian families are taking back power from these big tech companies," he told ABC TV on Wednesday.
"One of the dynamics that has occurred over a period of time is people being addicted, effectively.
"It won't be simple. It'll be a difficult period."
Under the changes, social media platforms will need to take reasonable steps to stop anyone under 16 having an account.
Tech companies are expected to use a range of methods to verify a user's age, including face scans with artificial intelligence, sophisticated analysis of people's posting patterns and language, and digital IDs.
Some platforms such as YouTube will still be accessible without an account, but it will be harder for algorithms to target content to children.
eSafety Commissioner Julie Inman Grant, who is responsible for enforcing the ban, said her agency would ask platforms to detail about how many children they'd booted off.
"There could be some... teething issues. Some will do it better than others," she said.
Teenager Nick Leech is one of those having his access revoked.
The 15-year-old says he's most worried about how he will stay in touch with friends who live interstate.
"I mainly use Snapchat to text them and talk to them, as well as stuff like Instagram and Facebook to know what's happening in their lives," he told AAP.
The teenager from regional Victoria is taking part in a study run by the Murdoch Children's Research Institute and Deakin University, which will track how the ban impacts young people.
"(Social media) has become such a big part in people's lives, and ... taking that away so suddenly is going to definitely cause some issues," Nick said.
The ban has also been subject to last-minute changes: a month before taking effect, social media platform Reddit and streaming site Kick were added.
Little-known apps Lemon8 and Yope have also been warned they may be included, because children were flocking to them in a bid to dodge the restrictions.
AAP has heard from dozens of parents who are deeply divided on whether the new rules are an important safety measure or an overreach which takes away the rights of families to choose how they raise their children.
Abby Howells, a Canberra teacher who has two boys aged 18 and 15, said she was hopeful the ban would help younger children, but only if it can't be circumvented.
"I feel like my kids did this big experiment, you had this phone stuff ... no one knows what it's going to do to them," she said.
