Netflix is testing a feature which may lead to a crackdown on users sharing their passwords.
Some users reported being met with a screen reading: "If you don't live with the owner of this account, you need your own account to keep watching."
Viewers are reportedly given the option to verify their identity through a code sent to the account's owner, or can choose to complete the process later.
In a statement, Netflix said: "This test is designed to help ensure that people using Netflix accounts are authorised to do so."
Netflix has previously said it was comfortable with users sharing their passwords.
Speaking in 2016, CEO Reed Hastings said the company had "no plans" on a crackdown.
He said: "Password sharing is something you have to learn to live with, because there's so much legitimate password sharing, like you sharing with your spouse, with your kids. So there's no bright line, and we're doing fine as is."
According to the Netflix terms of service, account details should "not be shared with individuals beyond your household".
In January the company, boosted by months of lockdown, revealed it had more than 203 million subscribers, making it the world's leading streaming service.