YouTube has ramped-up rules regarding when it will run ads with videos as it scrambled to quell concerns by brands about being paired with troublesome content.
"There's no denying 2017 was a difficult year, with several issues affecting our community and our advertising partners," YouTube vice president of display, video and analytics Paul Muret said in a blog post.
"The challenges we faced in 2017 have helped us make tough but necessary changes in 2018."
Channels at YouTube will need to have at least 1,000 subscribers and 4,000 hours of watch time within the past year to be eligible for ads, according to Muret.
Previously, channels could be eligible for ads as part of a YouTube Partner Program by racking up 10,000 views or more.
"We want to take channel size, audience engagement, and creator behaviour into consideration to determine eligibility for ads," Muret said.
YouTube will closely watch for spam, abuse flags and other signals to make sure channels are remaining within the Google-owned video-sharing platforms policies regarding content, according to the post.
Muret said that manual reviews of video will be added to a Google Preferred system that brands use to place ads with popular YouTube content to better vet videos.
YouTube is also providing advertisers simpler controls regarding where ads appear and transparency including safety checks by outside parties, according to Muret.
The changes were expected to affect "a significant number" of YouTube channels eligible to run ads.
YouTube late last year pulled 150,000 videos of children after lewd comments about them were posted by viewers and went public with a vow to greatly increase the ranks of workers focused on rooting out content violating its policies.
The moves came as YouTube strived to assure companies their ads would not appear with offensive or inappropriate videos.
"We are passionate about protecting our users, advertisers and creators and making sure YouTube is not a place that can be co-opted by bad actors," Muret said.
"While we took several steps last year to protect advertisers from inappropriate content, we know we need to do more to ensure that their ads run alongside content that reflects their values."