TL;DR stands for too long; didn't read and emerged as forum and message board slang in the early 2000s before spreading to Reddit, Discord and social media comments. It was first used as a reply to posts considered too lengthy to finish, then also as a way for writers to introduce their own short summary. As reaction culture grew, the phrase moved from typed comments into spoken edits and soundboard clips, where it now works as a standalone punchline for anything overly long or detailed.