An imbalance on a footprint chart is a price where one side traded much more than the other side at the next price. When several of them line up, you get a stacked imbalance.

Diagonal comparison

Footprint imbalances are measured diagonally. Ask volume at one price is compared with bid volume at the price below. If buyers traded three times more, that is a buying imbalance.

Stacks

Three or more buying imbalances in a row means buyers were lifting offers aggressively across a range of prices. Sellers could not keep up. The same applies in reverse for selling stacks.

How to use them

• Initiative: a stack in the direction of a breakout is confirmation that the move is real.

• Future levels: the zone of a stack often acts as support or resistance on a retest.

• Failed stacks: if price returns through a stack quickly, the initiative failed. That can be a strong signal the other way.

Practical tips

Settings matter. A ratio of 3:1 and a minimum volume filter keep the noise down. In thin overnight markets, stacks are less meaningful than during the main session.

In HOC Charts

The Stacked Imbalance indicator highlights stacks and can extend them as zones to the right, so you can see when price comes back to test them.