Order flow, without the trading-room mystique.

What order flow actually means

Order flow is the granular record of how trades get executed: who is hitting bids, who is lifting offers, where resting limits sit, and how aggressively the book is being consumed. On centralised exchanges it is visible through the depth of market and time and sales. In spot forex — which is decentralised — what you see depends entirely on which venue your data feed touches.

The reason traders care: every candle on a chart is a summary of thousands of those interactions. Two candles can look identical and tell completely different stories about who actually controlled the price during that bar. Order flow is an attempt to read the story behind the candle.

Bid, ask, and the spread

At any moment, the market shows a best bid (the highest price someone is willing to pay) and a best ask (the lowest price someone is willing to sell at). The gap between them is the spread. Resting limit orders sit at and around these prices, waiting to be filled. Market orders eat through them.

Two ways an order can interact with the book matter:

• Aggressive (taker) — a market order that crosses the spread and fills against resting orders. A buyer lifting the ask is an aggressive buy. A seller hitting the bid is an aggressive sell.
• Passive (maker) — a limit order resting in the book, waiting to be filled. Passive participants set the price; aggressive participants move it.

Price only moves when aggression overwhelms the passive side. If aggressive buyers eat through every offer in the book faster than new ones can be posted, the ask climbs. If the passive side restocks fast enough to absorb the aggression, price stays put. That tension is the whole game.

Aggressive vs passive prints

Most order flow software classifies each printed trade by which side initiated it. A trade printed at the ask is treated as an aggressive buy; a trade printed at the bid is treated as an aggressive sell. The classification is a heuristic, not perfect, but it captures most of what matters.

Why it matters: a big up candle with most of its volume transacted at the bid (i.e. aggressive selling that the passive side absorbed and then lifted) tells a very different story than a big up candle where volume was almost entirely hitting the ask. One is buyers chasing; the other is buyers defending.

Delta and cumulative delta

Delta is a single number: aggressive buy volume minus aggressive sell volume over a defined window (a candle, a minute, a session). Positive delta means buyers were the more aggressive side. Negative delta means sellers were. Zero means it was even.

Cumulative delta strings these values together over time, producing a line you can plot alongside price. The most useful signal is divergence: price prints a new high while cumulative delta makes a lower high. That means each new push higher required less buying aggression than the last — a weakening foot on the accelerator. The reverse holds on lows.

Reading delta divergence
  Bar 1   Price high: 1.0840   Delta: +1,820
  Bar 2   Price high: 1.0852   Delta: +1,240
  Bar 3   Price high: 1.0859   Delta:   +480
  => buyers are running out of aggression at higher prices

Divergence is a warning, not a signal. It tells you the move is being driven by less and less aggression. What it does not tell you is when the reversal will happen — that still requires structure.

Absorption and exhaustion

Absorption happens when one side of the book swallows aggressive flow without letting price move. Imagine persistent, heavy aggressive selling hitting the bid at a single price, and the bid simply refuses to break. Someone passive on the bid is absorbing the sellers. When the aggression dries up, the absorbed inventory can flip the short-term direction.

Exhaustion is the related cousin: a final spike of aggressive flow that fails to make new ground. High volume, big delta, tiny price progress. It often marks the end of a leg.

What this looks like in MT5

MT5 does not show you a centralised depth of market for spot FX. What it shows is your broker's tick volume and, on some configurations, the broker's liquidity provider ladder. Tick volume in forex counts price updates, not real contracts — it is a proxy for activity, not actual traded size.

Inside that constraint there are still useful things you can do:

• Compare tick volume across bars at key structural levels. A breakout on half the activity of the prior leg is suspect.
• Watch the spread around news and session changes. Spread widening means liquidity providers are stepping back; aggressive entries into those windows cost a lot more than the chart suggests.
• Use candle anatomy as proxy flow. Long upper wicks into resistance with high tick volume look like absorbed buying even without a real DOM. Treat the inference as soft evidence, not proof.

An honest disclaimer

Putting it together

Order flow is a confirmation tool, not a setup generator. Build your trade idea from structure and liquidity, then use flow to ask: is the move being chased or absorbed? Is delta confirming the direction or quietly diverging? Is volume expanding into the level or shrinking? When the answers agree with your structural read, you have alignment. When they disagree, you have a reason to wait.