Sweeps and big lots in order flow
Most trades are small. Now and then one participant shows their hand with a single large order, or with an order so urgent it takes every price in its way. Those are big lots and sweeps, and they are some of the clearest prints in the tape.
What a sweep is
A sweep is an aggressive order that is too large for the best price alone. It fills everything resting at the best bid or offer, then keeps going into the next price and the one after that, all in the same instant.
A sweep says more about urgency than about size. The trader behind it chose to pay several ticks of slippage instead of waiting, which usually means they wanted in or out right now.
What a big lot is
A big lot is a single trade far larger than the usual trade size for that instrument and session. On a busy index future, most prints are a handful of contracts, so a trade of dozens or hundreds stands out.
Size alone is relative. A lot that is large at lunchtime can be ordinary at the open, so big lots are best judged against the session's own trade sizes rather than against a fixed number.
Runs, not single prints
Large participants often split an order into several pieces a few seconds apart. Seeing three big sell lots in a row across a few ticks tells you more than any one of them. Grouping a run of prints into one line, with the price range and the total, keeps the picture readable in a fast market.
How to read them
- Note the side: a sweep or big lot at the offer is aggressive buying, at the bid aggressive selling.
- Check where it happened: at a level that matters, or in the middle of nowhere.
- Watch what price does next. A big lot that is followed by more pushing is different from one that gets absorbed.
- Look at the dollar value as well as contracts, especially when comparing instruments with different contract sizes.
What they do not tell you
A large print shows that someone traded size, not why. It can be a new position, a hedge, or someone closing out. Treat sweeps and big lots as evidence about who is active, read next to pressure and price, not as a signal on their own.
How Delphi Pulse shows it
Delphi Pulse lists sweeps and big lots with the time, side, price, contracts and dollar value. A run of prints is grouped into one row with its price range, the size thresholds can be changed in settings, and the list folds to the newest row so it stays out of the way. An optional sound can mark each one.
Rendered from a replay with sample prices, to explain how the add-on works. Not a trade result.
Learn about Delphi PulseMore order flow guides
What is absorption in order flow?
Absorption is when aggressive orders keep hitting a price and it does not move. Learn how to spot it, why it matters and how to tell it apart from a push that works.
How to read buyer and seller volume pressure
Volume pressure measures how much aggressive buying and selling is trading right now compared with normal. Learn what it shows, how to read it and where it misleads.
Effort versus result in order flow
Effort versus result compares how much volume a push takes with how far price moves. Learn how it separates pushes that move price from pushes that stall or get absorbed.
ES vs NQ: which index is leading?
ES and NQ usually move together, so it matters when one pushes and the other does not. Learn how to compare their order flow and read which index started first.
Reading ES order flow for SPX 0DTE options
SPX has no order book of its own, but ES futures do. Learn how SPX 0DTE options traders use ES order flow and how to convert ES prices to SPX levels.
This guide is for educational purposes only, about how markets trade and how an analysis tool displays it. It is not financial advice and does not recommend buying or selling any futures or options contract. Trading futures and options involves substantial risk, and losses can exceed the amount committed. See the Terms of Service.