'Reaction' videos have become a phenomenon on YouTube, with The Fine Brothers having made a name for themselves producing the popular videos.
However, The Fine Brothers have now caused an outcry amongst fellow You Tubers as they have tried to trademark the term 'react'.
It will be interesting to see whether The Fine Brothers have a case or if they are simply trying to get a reaction from the You Tube community.
The creators of one of YouTube's biggest channels have sparked fury over plans to trademark and license a popular video format. The Fine Brothers produce a popular series of "reaction videos", in which people watch online clips and respond. On Tuesday, they revealed a scheme to let other video-makers use assets from their version of the format. But they have faced a backlash from viewers for trademarking "react" - a term widely used by other creators.