DOM Reading Fundamentals: Order Book Structure and Workflow

The Depth of Market (DOM) ladder lists resting limit orders: bids below price, offers above. Each row shows a price and the size waiting there. The middle — best bid and best ask — is the spread. Reading the DOM is a structured workflow, not a glance.

The four elements to scan

1. Spread: the gap between best bid and best offer. One tick = liquid, competitive. Three-plus ticks = illiquid or fast-moving; slippage risk rises. Sudden widening signals a news shock or market-maker withdrawal — stand aside.

2. Size imbalance: compare total size in the top 5 bid levels vs top 5 offer levels. A persistent 3:1 bid-heavy imbalance for several minutes often precedes upward moves; offer-heavy precedes downward. But large visible size is frequently spoofed — never act on size alone.

3. Order flicker (pulling/refreshing): watch whether large orders hold or vanish as price approaches. Orders that disappear before fills are spoofs. Orders that refresh after fills are icebergs. Orders that get consumed are real liquidity.

4. Aggression (the tape): market orders hitting bids (sells) or lifting offers (buys) print on the time and sales tape. Heavy offer-lifting with no price advance = absorption (sellers absorbing). Heavy bid-hitting with no decline = absorption (buyers absorbing).

A repeatable reading workflow

Every 30 seconds, run this scan:

1. Read the spread — is it normal or widening?
2. Sum top-5 bid size vs top-5 offer size — which side is heavier?
3. Note any large orders within 3 ticks of price — are they holding or flickering?
4. Glance at the tape — is aggression one-sided?
5. Compare to price action — is aggression moving price or being absorbed?

A divergence — heavy aggression with no price movement — is the highest-value DOM signal. It flags absorption, the precursor to many reversals.

Execution rules

• Use limit orders when resting size is real (holds as price approaches) — you earn the spread and avoid slippage.
• Use market orders only when speed matters and the book is deep (large resting size on your side).
• Never enter against a 5:1 size imbalance without tape confirmation of absorption.

The DOM rewards a disciplined scan over reaction. Build the four-element workflow into muscle memory before adding iceberg and spoof detection. Read structure first; trade the divergences it reveals.