The company currently shares ad revenue with video-makers who are enrolled in its partnership scheme, when it shows ads before or during their content.
But YouTube says it will start putting ads on some videos from channels that are not part of its partnership scheme.
Changes to its terms of service mean YouTube will not share the revenue from those ads with the video-makers.
It could also mean viewers see a higher number of adverts across the site.
YouTube's Partner Programme is something that has to be applied for, and is only available to channels that have more than 1,000 subscribers and have clocked up 4,000 hours of people watching in a year.
YouTube said channels not in the programme would not "receive a share of the revenue from these ads" though the makers would have the opportunity to apply for YPP as normal if they met the eligibility requirements.
But YouTube's own explanation of the application process says applications are put in a queue to be reviewed by humans, which can take more than a month.