Last year was a tricky one for YouTube, by its own admission. It faced issues with "brand safety," where big-name ads from companies including Mars, Adidas and Deutsche Bank were running against videos showing violent or other inappropriate content.
Then at the start of 2018, it put a partnership with top content creator Logan Paul on hold, after he posted a video of a suicide victim in Japan.
From February 20, YouTube will start to remove smaller channels that currently run ads, according to a blog post by Paul Muret, its vice-president of display, video and analytics.
At the moment, channels have to reach 10,000 total views to be in YouTube's Partner Program (YPP), but under the new rules they will need to have at least 1,000 subscribers and 4,000 hours of watch time to be eligible to run ads.