Reading an order book

Two lists of intentions. Where they thin out is where price moves fastest.

An order book is simply every resting limit order on one exchange, sorted by price. Bids are what buyers are willing to pay, asks are what sellers are willing to accept, and the gap between the best of each is the spread.

The three things worth reading

1. Spread

A narrow spread means an active, liquid market where entering and exiting is cheap. A wide spread means every trade costs you before it starts. On the same pair, the spread widens sharply during volatility — which is why entering in the first seconds of a spike is expensive.

2. Depth

How much size sits within a percent or two of the current price. Deep books absorb large orders quietly; thin books lurch. This matters more than the fee schedule for anyone trading meaningful size.

3. Imbalance

The ratio between resting bids and asks. Our book pressure panel shows this as a coloured bar: heavy bids suggest buyers are willing to be patient at these prices, heavy asks the opposite.

Practical uses

1. Sizing. If your intended order is a large fraction of the visible depth, split it or trade elsewhere.
2. Placing limits. Resting just inside a thick band of orders tends to fill; resting behind it often does not.
3. Recognising thin conditions. A book that suddenly empties is a warning that the next order will move price a long way. This is exactly when stop-market orders fill badly.

What the book cannot tell you

An order book shows resting limit orders. It does not show intention, and the gap between those two things is where beginners get hurt.

• Orders can vanish instantly. A large visible wall can be cancelled in the same second price approaches it. Some are placed specifically to be seen and then pulled — the practice is called spoofing and it is illegal in regulated markets and routine in unregulated ones.
• Iceberg orders hide size. A displayed order of ten units may represent a thousand, refreshing as each slice fills. The book understates real depth in these cases.
• Market orders are invisible until they arrive. The largest source of movement never appears in the book at all.

Reading depth properly

The useful question is not "are there more bids or asks" but "how far does price move if someone sells my size right now". That is a measurable thing, and it is what our exit test panel calculates by walking the book with your quantity.

Three practical readings:

1. Cumulative depth within 1%. If total resting bids within one percent of price are smaller than your position, you cannot exit at market without moving the market.
2. The shape of the ladder. Smooth, evenly distributed liquidity means a healthy market. A book that is empty for several levels then has one enormous order is fragile — remove that order and there is nothing underneath.
3. How the spread behaves under stress. A spread that widens dramatically on ordinary moves tells you market makers do not want the risk, which is a warning about the venue as much as the asset.

Book pressure across timeframes

The imbalance figure in our book panel is a snapshot. Its value comes from watching it change rather than reading it once.

Persistent heavy bids while price grinds sideways often means accumulation — someone is willing to be patient at these prices. Bids thinning out while price holds up is the opposite and considerably more dangerous, because the support you can see is being quietly withdrawn before anything visible happens to price.

Pair it with the taker flow panel, which shows who is hitting the book aggressively. Resting orders show patience; taker flow shows urgency. When they disagree — heavy resting bids but aggressive selling — the aggressive side usually wins in the short run.

Using the book before you trade

1. Check depth against your size before every entry of meaningful size. This single habit prevents most slippage complaints.
2. Place limits just inside clusters, not behind them. An order resting behind a thick band frequently never fills.
3. Avoid the first seconds of a violent move, when the book empties and spreads widen — orders placed then fill badly.
4. Compare venues for the same pair. Depth varies enormously, and the exchange volume panel shows where the real book lives.

Common questions

Is a big buy wall bullish?

Not reliably. It may be genuine demand, or it may be placed to encourage buying and cancelled before it fills. Watch whether it actually absorbs selling when tested — a wall that holds through real selling is information; one that vanishes was theatre.

Why does the book look different on each exchange?

Because each venue matches its own participants. Depth, spread and even price differ, which is why the exchange spread panel exists — a move visible on one book and not others is that venue, not the market.

Can I see stop orders in the book?

No. Stops are conditional instructions held by the exchange and only become visible orders when triggered. That is precisely why they cluster invisibly at obvious levels, and why the stop-hunt map estimates them from structure instead.