Order flow

Updated August 2026

Order flow is a phrase that gets used loosely, often as a stand-in for a trading style or a paid overlay. Underneath the marketing it is a plain idea: read the order book and the trade tape together, and you can see both what size is posted and which side is actually taking it. This page defines the concept and links to each measurable part.

The book and the tape

There are two things happening in a market at once. The book is the set of resting orders waiting to be filled: size posted at prices, on the bid and on the ask, that has not traded yet. The tape is the stream of trades that actually executed. Order flow is what you get when you stop looking at either one alone and read them against each other.

The distinction matters because the two can disagree. The book can lean heavily to the bid while the tape shows the sell side taking most of the liquidity. Neither is wrong; they measure different things. Order flow is the habit of holding both in view, which is why it is best treated as a set of measurements rather than a single score.

The measurable parts

BlackForge does not sell an order-flow score. It sells the components, each measured per pair per closed five-minute window, and you read them together. There are four:

• The executed side: taker buy and sell volume and counts, average and largest trade size per side, from the tradeFlow family.
• The size dimension: counts and volumes of trades that were large multiples of the average size, split by aggressor side, from the strong family.
• The book side: depth bands and seven-rung order ladders on each side, from the bookWalls and orderLadders families.
• The behaviour side: liquidity added and removed, level flicker, and median resting-level lifetime, from the bookMicro family.

What it looks like in real data

Here are four order-flow columns for BTCUSDT on binance in the latest window, touching both sides of the picture: taker buy and sell value from the tape, and the counts of outsized taker-buy and taker-sell trades. The volumes are in quote value and the strong counts are plain counts, so they are shown as a labelled readout.

What order flow tells you, and what it does not

Read together, these columns describe the balance of activity in the window: how much was posted and where, how much traded and from which side, and whether the large trades leaned one way. That is a richer description of what happened than price and volume alone, because it separates the resting book from the executed tape and the ordinary trades from the outsized ones.

What order flow is not, here, is a predictive product. BlackForge does not score it, rank it, or turn it into a buy or sell arrow. Every column is a measurement of a closed window, and the positioning rule is deliberate: the reading is yours to make.

The component definitions

Each part of order flow has its own definition. Taker buy and sell volume covers the executed tape by aggressor side; order book depth covers the resting book; order book imbalance covers the asymmetry between the two sides; liquidity added and removed and resting order lifetime cover how the book churned. The full metric reference lists all of them with their units and plans.

See the full metric reference, or browse the glossary.