Guide
What is an order book heatmap?
A candlestick chart tells you where price has been. An order book heatmap tells you what price had to get through to be there — and what is waiting above and below it right now.
The chart has three layers
Every order book heatmap is really three different data sources drawn on the same grid, and it helps to keep them apart in your head.
1. Resting liquidity — the heat
The coloured background is the order book itself: limit orders waiting at each price. Brighter means more size resting there. Nothing in this layer has traded. It is a picture of what people say they are willing to do.
2. Executed trades — the bubbles
Each trade that actually happened is drawn at its price and time, sized by how much went through. This is the aggressive side of the market: someone who wanted in or out now, and paid the spread to get it.
3. Price — the line
The thin line walking through the middle is the mid price. On its own it is the least interesting layer. It becomes interesting when you can see what it walked through.
How to read it
Three patterns come up constantly, and they are the reason the chart is worth looking at.
A wall that holds
A bright band sits above price. Trades hit it repeatedly — you see bubbles stacking at that level — and the band stays bright. Someone is refilling. Price stalls and turns away. The seller had more size than the buyers had aggression.
A wall that breaks
The same picture, except the band dims as the bubbles land on it, and then vanishes. Price continues through. The order was consumed rather than refilled, and whatever was behind it was thin.
A wall that disappears untouched
The band vanishes without trades landing on it. Nobody bought it — it was pulled. That is a different signal entirely, and it is invisible on a normal chart.
The honest caveat. A large resting order is not a promise. It can be cancelled in a millisecond, and a market can be moved by orders that were never meant to be filled. Size that gets traded is evidence. Size that is only displayed is a claim.
Why the time axis matters
A depth chart — the ladder you see on most exchanges — shows the book right now. A heatmap shows the same book over time. That difference is the whole point: you can see that the level which is stopping price today has been defended for two hours, or that it appeared thirty seconds ago.
Reading the scale honestly
Most heatmaps compress the price axis into bins and the colour scale logarithmically, because the largest orders are often hundreds of times bigger than the typical one. That means colour is relative, not absolute. Before you conclude that a level is huge, check the actual size — a good tool shows it in the units the market trades in.
See it on live data. Swiftedge Depth shows the Bitcoin futures order book as a heatmap with every trade as a bubble, free in the browser and with no sign-up.
Common questions
What does an order book heatmap show?
It shows resting limit orders — bids and asks that are waiting to be filled — as colour on a price and time grid. Bright areas are large resting size at that price. As time moves left to right, you see the same orders sitting, growing, or disappearing.
What is the difference between a heatmap and volume?
A heatmap shows intent: orders that are waiting. Volume shows what actually traded. Both matter, and they answer different questions. Size that sits and is never traded is very different from size that gets eaten in seconds.
Is an order book heatmap useful for crypto?
Crypto order books are public and update continuously, which makes them well suited to this kind of chart. Bitcoin futures on a large exchange update several times a second, so a heatmap can show a level forming and being taken out within the same minute.