That's BS is a piece of internet shorthand for calling out something unbelievable, exaggerated or plainly false, and short spoken versions of it have become a staple reaction on soundboards, streams and short-form edits. Creators tend to reach for it when a clip needs a quick, no-nonsense verdict rather than a long explanation, because the phrase is instantly understood even without context. Its eight-second length also makes it easy to drop into gaming videos, reaction content and meme compilations without breaking the pace of the edit.