YouTube will turn off commenting on videos with children after a vlogger claims to have found pedophile cases targeting videos of young girls on the site.
The video sharing platform said it has suspended comments from tens of millions of videos over the past week that "may be at risk of attracting predatory behavior."
American vlogger Matt Watson, who runs the MattsWhatItIs channel, said he discovered a "wormhole" in a "soft-core pedophile ring."
In a video posted on the platform, he said that pedophiles were providing links to child pornography, sharing contact details and swapping unlisted videos in the comment sections below the videos.
Many of the targeted videos are "innocuous" and cool, showing kids doing daily activities at home.
Watson also claimed that the site's "recommended" feature, which directs users to similar videos, was "making" predators' ability to connect with each other.
Companies such as Nestlé and the maker of Fortnite Epic Games have withdrawn their advertisements on the site after complaints.
In a statement on its Creators Blog, YouTube said it was taking "important steps" that are "crucial to keeping young people safe," and would continue to identify videos at risk.
The statement said: "In the coming months, we will expand this action to suspend commentary on videos of younger youth and videos showing underage children who might be at risk of attracting predatory behavior."
YouTube added that a "small number of creators" would be able to keep comments, but would need to actively monitor and show that they were "at low risk of predatory behavior."
The platform is also introducing a new "comment classifier," which will be able to detect and remove twice as many predatory comments as the current system.
This is not the first time YouTube has been reviewed for content with children.
In 2017, Mars and Adidas removed advertising from site after activists warned that pedophiles were targeting children's videos.
An investigation in The Times revealed that predators left obscure comments and tried to encourage children to post videos to participate in private discussions through online forums.
After the reaction, YouTube said it "hardened" its approach to videos and comments about children and was "committed to doing it right."
Last week, YouTube announced that it has closed more than 400 channels in 48 hours in an aggressive approach, in addition to the usual protections.