Absorption is aggressive orders meeting resting size and failing to move price. Buyers keep lifting the offer, the offer keeps being there, and the market goes nowhere. It is the single most useful thing a heatmap shows you, because it is the moment a level stops being a guess and becomes evidence.
Three ingredients, all required
Absorption is not one observation, it is three happening together. Miss any of them and you are looking at something else.
- Resting size. A wall is holding at the level, and it is still holding.
- Aggression arriving. Market orders are actually hitting it. On Bookmap these are the trade dots, sized by volume, stacking up at that price.
- Price not moving. The level takes the flow and the market does not advance through it.
Size with no aggression is just an order sitting there. Aggression with no size is a market breaking through thin liquidity. Both together with price stuck is absorption.
These two pictures start identically. The difference only appears in the last third, and that is the part worth waiting for. Anyone can see a large offer; the trade is in whether it holds.
A wall tells you where somebody says they will trade. Absorption tells you they actually did, repeatedly, against pressure. That is the difference between a claim and a demonstration, and the market only pays for the second one.
What follows absorption
Two things can happen after a level absorbs, and both are tradeable if you know which you are watching.
The aggressors give up. Buyers who have been lifting the offer for a minute without progress stop, and some of them exit. Their exit is selling, which is now hitting a market with no buyers left to fight. This is the reversal case, and it is the one most people mean when they talk about absorption.
The absorber finishes. The resting order fills completely and is not replaced. There is now nothing above, and all that trapped upward pressure meets a thin book. This is the continuation case, and it is why absorption is not a reason to fade blindly.
You do not know which until the level either holds and pressure fades, or clears and price accelerates. Watching for that resolution is the skill; predicting it from the wall alone is not.
Price standing still on almost no volume is not a level taking pressure, it is nobody trading. Absorption requires the aggression to be real. If the trade dots are sparse and small, price is not being held, it is simply not being pushed.
Reading the aggression, not just the wall
The heatmap draws resting liquidity. The trades arriving are drawn on top of it, and the two together are the point. On Bookmap the dot size is the trade size, so a run of large dots piling into one price while the colour there stays bright is the picture you are looking for.
What you want to see is volume going in and price not coming out. If you find yourself explaining why a level is significant while the tape is quiet, there is no absorption happening, only a level you like the look of.
Absorption reads most cleanly at levels that already mattered for another reason: a value area edge, an overnight high, a prior session's point of control. Liquidity resting at a level the rest of your analysis already flagged is confirmation. Liquidity resting at a random price is one participant's opinion.
Failed absorption is information too
When a level that has been holding suddenly clears, the participants who were leaning on it are wrong and have to do something about it. That is why breaks through well-defended levels are often faster than breaks through empty ones: the move has both the original pressure and the exit of everyone who bet against it.
So a wall that fails is not a wasted observation. It marks the price where a group of people were proven wrong, and their reaction is frequently the cleanest part of the move.
Volume arriving and price refusing to move is the market telling you who is winning. Volume arriving and price moving is the same sentence with the other answer.