Popular YouTubers the Fine Brothers, known for creating the "reacts" videos, in which people react to being shown certain things, have sparked outrage for attempting to trademark "react," a word that is widely used by other content creators around the Internet.

Typically, the "react" videos involve showing a particular group of people, like seniors or kids, an online video or object and then discussing it. The format has become hugely popular and has even been used on talk shows like Ellen.

The format has been particularly successful for the Fine Brothers, Benny and Rafi, who have come up with a number of series, including Kids React, Teens React and YouTubers React. Last year, however, the duo trademarked terms like "Kids React," "Celebrities React" and even the word "react" itself. 

They then announced a scheme for licensing called "React World," which would allow content creators to use assets like graphics and music for their own reaction videos. However, this was negatively received because so many people use the term "react" in their videos.

The Fine Brothers, however, suggest that they only plan to license a full package of content for the react videos — meaning that simply using the word "react" won't garner any attention from them. Despite this, a number of content creators have claimed that the Fine Brothers have already had some content removed.

"They've used their leverage with YouTube to take down channels that were making kids react videos and seniors react videos," said one critic on Reddit.

To clarify, however, the Fine Brothers have said that they are not trademarking reaction content in general, just trademarked names like "Kids react to ..."

Ryan Morrison, a lawyer, has expressed his disapproval of the scheme and has said that he will help YouTubers fight against the trademark application, and that the public has 30 days to file an opposition to the application.