Sweep Detection

What is Sweep Detection?

Sweep detection is the order-flow practice of reconstructing sweeps from the tape: aggressive executions that consume resting liquidity across several price levels almost simultaneously. On time and sales, a sweep appears as a burst of same-direction prints at successively higher (or lower) prices within a very short window, often milliseconds, as one marketable order walks through the book. Detection logic groups prints by timestamp proximity, aggressor side, and stepping price, then merges them into a single event with a total size.

A sweep signals urgency: the participant chose immediacy over price, accepting slippage to be filled now. In US equities and options the related intermarket sweep order routes across venues simultaneously, and large option sweeps are widely tracked as urgency prints. Note the naming collision: this microstructure event is not the Smart Money Concepts liquidity sweep, which describes price running stops beyond a swing level rather than an execution style.

How traders use it

• As confirmation of initiative: repeated same-direction sweeps into or through a level suggest aggressive participants are driving, which supports breakout and continuation reads better than passive drift does; many combine this with tape reading or delta tools.
• As an urgency screen against size alone: block trades are large but often negotiated and patient, while a sweep of comparable size implies someone paid up for speed, which is usually the more informative fact.
• As an alert primitive near levels: sweeps firing at a prior high or low, a VWAP, or a value-area edge flag urgent activity exactly where it matters. The read stays probabilistic: a sweep proves aggression, not intent, and can be a hedge or an exit as easily as new positioning.