That's class is a common slang compliment in Ireland and parts of the UK, where class is used to mean excellent, impressive or top quality rather than social rank. As short voice reactions spread on video platforms and soundboards, the phrase became a handy standalone clip that needs no context to understand. Its brevity and upbeat tone helped it travel into gaming edits, sports highlights and group chats, where it functions as instant praise. It remains popular because the wording is distinctive, positive and easy to reuse across many situations.