Footprint charts

A footprint chart (also called a cluster or numbers-bars chart) takes a normal candle and opens it up to show what traded inside it at each price — not just OHLC, but the volume done at the bid versus the ask at every level within the bar.

What a footprint cell shows

Each price row inside a bar typically displays two numbers: volume that executed at the bid (aggressive selling) and at the ask (aggressive buying) at that price. A common layout:

Price    Bid x Ask
1.2510    12 x 480     <- buyers dominant
1.2509    35 x 120
1.2508   210 x  44     <- sellers dominant
1.2507   330 x  18

This lets you see, within a single candle, where buying and selling actually concentrated — invisible on a normal chart.

What people read from it

• Delta — net (ask volume minus bid volume) per level or per bar, summarizing whether aggressive buyers or sellers dominated.
• Imbalances — a lopsided ratio between the bid and ask volume at adjacent prices (covered in its own lesson).
• Point of control of the bar — the price with the most volume inside the candle.
• Absorption/exhaustion made visible: heavy bid volume with no downside progress, etc.

Honest caveats

• Footprint needs trade-level data with aggressor classification — so it is a centralized-market tool (futures, some equities). In spot forex it is at best approximated from a broker feed and should be treated with suspicion.
• It is dense. It rewards a specific, slower style and overwhelms most traders on fast instruments. It is a study tool, not a fast-twitch one.