How to read an order book (DOM): liquidity, walls, spoofing and icebergs

The order book, often called the DOM (Depth of Market), lists every resting limit order on a market: on one side those who want to buy (the bids), on the other those who want to sell (the asks or offers). It is the only window showing participants’ intentions before they turn into trades.

How the book is structured

• Best bid: the highest price someone will buy at right now.
• Best ask: the lowest price someone will sell at right now.
• Spread: the gap between the two. On BTC/USDT it is often a single tick; on a thin market it can be wide, which makes every round trip more expensive.
• Depth: the total quantity resting at each level. The deeper the book, the more volume it takes to move price.

In the Bullmarket terminal, the DOM also shows, for each price, the volume actually traded and recent aggressive buys and sells: you see both what is offered and what is done.

Passive versus aggressive orders

The book only contains passive orders. Price only moves when aggressive (market) orders consume that liquidity. A simple rule follows: liquidity does not push price up or down, it slows it down. Aggressors are what move it. Reading the DOM means watching those two forces meet.

Liquidity walls

A “wall” is a level where the displayed size dwarfs its neighbours — say 300 BTC bid at 60,000 while other levels show 5 to 10. The instinct is to treat it as support. Sometimes it is, but three scenarios are possible:

1. The wall holds: aggressive sells crash into it and price bounces. Time & Sales shows lots of selling at that price without the level giving way: that is absorption.
2. The wall gets eaten: the size shrinks trade after trade until it vanishes, and price speeds up to the downside because sellers have cleared the last obstacle.
3. The wall disappears before being touched: it was there to impress, not to be filled.

Spoofing and phantom orders

Spoofing means placing large orders you never intend to fill, to fake buying or selling pressure, then cancelling them just before price gets there. It is illegal on regulated markets (in the United States explicitly since the 2010 Dodd-Frank Act; in Europe under the Market Abuse Regulation). Surveillance on crypto venues is more uneven, which calls for a cautious rule: a displayed order is only an intention, revocable at any moment.

How to protect yourself? Never decide on the book alone. A wall that steps back every time price approaches, or that keeps appearing and vanishing, is suspect. What matters is what actually trades.

Iceberg orders

The opposite of spoofing, an iceberg hides its true size. A large buyer shows 2 BTC at 60,000; as soon as they are filled, 2 new BTC reappear at the same price, again and again. The giveaway: Time & Sales shows far more volume executed at that price than the book ever displayed. It is a discreet form of absorption, and often a serious level.

Overall bid/ask imbalance

The bar at the bottom of the DOM compares total bid size and total ask size across the displayed levels. It gives a temperature of visible liquidity, not a direction: heavy bids may mean support… or simply that sellers are working with market orders that never show in the book. Use it as context, never as a trigger.

A 4-question reading routine

1. Where are the unusual liquidity levels close to price?
2. As price approaches, do the sizes hold, grow (reloading) or step back?
3. What does Time & Sales say: is volume really trading at that price?
4. Does the footprint confirm it (absorption, diverging delta)?

Only when three answers line up does an order-book level become usable information. Practise spotting these situations in the terminal, then trade them virtually in the simulator.