TL;DR started as an insult, too long; didn't read, and grew into the most useful convention in written communication: the part everyone reads. Which is exactly why it deserves more craft than the three bullet fragments it usually gets.
01Steal from the military: BLUF
Armed forces correspondence has a rule called bottom line up front: state the conclusion and the required action in the first sentence, then support it. Adopt it wholesale. If your document recommends something, the TL;DR's first line is the recommendation. If it reports something, the first line is the single most consequential finding. Never open a summary with background; background is what the rest of the document is for.
02One claim per line, in full sentences
The fragment habit, launch delayed, budget concerns, team aligned, feels concise but forces the reader to reconstruct your meaning, and three readers will reconstruct three meanings. Write complete sentences that each carry exactly one claim: the launch moves to October because the payment integration slipped. Anyone can forward that line on its own and it still says the right thing. That property, quotability, is the real test of a summary line.
03Numbers survive, adjectives do not
In a week, nobody remembers significant improvement; they remember 40%. Carry the two or three exact figures that the document's argument stands on, with their units and their comparison points. If the source says revenue grew from 1.2M to 1.9M, the TL;DR says that, not revenue grew strongly. When you must round, round visibly: about 60%, not most.
04Placement is half the craft
A summary at the end of a document is an epilogue. Put the TL;DR at the very top, visually distinct from the body, and keep it to three to five lines so it reads in under thirty seconds. That is the standard this site's own format, the 30-second version, is built around: answer first, structured lines, readable before the reader decides whether to continue. Where the summary sits determines who it serves.
How is a TL;DR different from an abstract?
An abstract describes the document; a TL;DR delivers its value. An abstract says this report examines Q3 performance; a TL;DR says Q3 revenue missed plan by 8%, driven by churn in the mid-market tier.
Should I write the TL;DR before or after the document?
Draft it first to force clarity about your point, then rewrite it last so it matches what the document ended up saying. The gap between the two versions is usually the most instructive edit of the whole piece.
How many bullets is too many?
Five. Past five lines, readers start skimming the summary itself, which defeats its purpose. If you cannot get under five, the document probably contains two documents.
Summarizing at volume, not one page at a time?
Summarize Pro batches PDFs, papers and reports, every key claim cited to its source page, exports to Word or Excel. The free tool is for one page; Pro is for the pile.