tl;dr
Published October 3, 2026
tl;dr, short for "too long; didn't read," is forum shorthand people drop under walls of text to say they skipped it, or tack onto their own posts as a one-line summary. First logged on Urban Dictionary in January 2003 and spreading through General Mayhem, 4chan and SomethingAwful that same year, the abbreviation grew into one of the most reused pieces of English-language forum slang and later gave Reddit its own /r/tldr digest.
Overview
People use tl;dr in two opposing modes. As a dismissive reply, a commenter drops "tl;dr" under a long post to signal they refused to read it, which readers who know the term often treat as spam or a lazy heckle3. As a courtesy, authors of long posts write their own "tl;dr:" line at the top or bottom, condensing a wall of text into a single summary sentence for skimmers.
The shorthand carries a built-in sneer about attention spans, and the Urban Dictionary entries from the mid-2000s lean into that, with one definition openly mocking the "lazy, ignorant" posters who type it instead of engaging3. That ambivalence, equal parts helpful summary tool and insult, is why tl;dr kept its charge even as it spread to Wikipedia talk pages1 and became a default section header on Reddit threads.
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Origin & Background
How It Spread
Timeline
How to Use This Meme
The common convention is one of two formats. Writers typically prefix a short summary with "tl;dr:" and place it at the very top or bottom of a long post so readers can skim before deciding whether to read the full thing. The dismissive form is just the four letters on their own, posted as a reply, which is why many communities treat a bare "tl;dr" as rude or low-effort3.