Trading term
What is Order flow?
Order flow is the study of actual transactions as they happen — which side is crossing the spread to get filled, and in what size. It looks at who is being aggressive rather than at what the price did.
Every trade has a passive side and an aggressive side. Someone rests an order on the bid or the offer and waits; someone else decides they want it badly enough to cross the spread and take it. Order-flow analysis classifies each print by which side initiated it, then aggregates: how much volume was bought at the offer versus sold at the bid, at each price.
The headline number is delta — buying volume minus selling volume. A candle can close green while its delta is deeply negative, which tells you the advance happened on passive buying rather than aggression, and is generally read as weaker. Footprint charts display this inside each candle, splitting every price into bid-side and ask-side volume.
This is the most granular view available on a chart, and it is genuinely different information from price. But it needs real transaction data — a proper futures or equities feed — which is why it is standard among futures traders and largely absent from retail forex and many crypto venues.
One candle split by price, bid-side against ask-side. Sellers were aggressive at every level for a delta of −1,200 — even though the candle closed up.
For example
A candle closes up $0.40 on 4,200 contracts. The footprint shows 1,500 bought at the offer against 2,700 sold at the bid — a delta of −1,200. Price rose, but sellers were the aggressive side the whole way; the advance was buyers passively absorbing, and it fails shortly after.
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Explore Premium →Why it matters to you
Price tells you the outcome; order flow tells you how it was achieved. A rally on strong positive delta and a rally on negative delta look identical as candles but mean different things about who is committed. That distinction is the main reason serious short-term traders pay for the data.
⚠ It's the most granular data and the easiest to over-read
Delta is noisy at small scales, and a single candle's imbalance means very little on its own — traders routinely talk themselves into reversals from one negative print. It's also easy to get wrong: 'aggressive selling' at a low frequently marks the exhaustion point, not the start of a decline. Read it in context, over sequences, not candle by candle.