What Is Order Book Imbalance?

Order book imbalance and volume delta are two different measurements.

Order book imbalance compares displayed buy and sell liquidity at selected price levels.

Volume delta generally compares executed volume classified as aggressive buying versus aggressive selling.

For example, the DOM may display more resting buy liquidity than sell liquidity, while recent executions show negative delta.

There is no contradiction: displayed orders and executed trades measure different things.

Displayed orders can change or disappear, while executed volume records transactions that have already occurred.

Neither measurement independently guarantees the next price movement.

I prefer to understand what each tool measures before combining the signals into a trading decision.