World's Richest YouTuber.
As of my knowledge cutoff date of September 2021, the world's richest YouTuber is currently considered to be Ryan Kaji, a nine-year-old boy who has built a massive following on his YouTube channel "Ryan's World." Ryan's channel began in 2015 as a toy-review channel and has since expanded to include other types of family-friendly content, such as science experiments, educational videos, and challenges.
According to Forbes, Ryan Kaji earned an estimated $29.5 million in 2020, making him the highest-earning YouTuber for the third year in a row. Most of his income comes from sponsorships, licensing deals, and merchandise sales, rather than just ad revenue from his videos.
It's worth noting that YouTube income can fluctuate greatly depending on a variety of factors, such as the number of views, the type of content, and the advertisers willing to pay for ad space. So while Ryan Kaji is currently considered the richest YouTuber, this could change at any time as other creators gain popularity or shift their focus to more lucrative revenue streams.