Thin book (liquidity void)
A thin book is an order book in which little resting size sits at the levels around the market, so that modest aggressive volume moves price several ticks. A liquidity void is the same condition seen as a gap: a stretch of prices with almost no displayed depth that price tends to cross quickly.
Senzoukria · Glossary · Updated September 2026
Definition and causes
Depth is what absorbs aggression. When the displayed sizes at the first levels are small relative to typical trade sizes, each market order exhausts a level and the next one becomes best. Price moves not because demand is large but because supply at each price is small.
Thin books appear around scheduled news, in the last minutes before a close, during holiday sessions, and on contracts far from the front month. They also appear briefly after a sweep, when the consumed side has not yet been replenished.
- Wider spread: with little size near the touch the best bid and offer sit further apart.
- Low cumulative depth: the sum of the first levels on one or both sides is small.
- Fast, gappy prints: trades appear at prices several ticks apart in quick succession.
How it looks in each view
- DOM ladder: short numbers on many consecutive rows, sometimes empty rows in the displayed range.
- Heatmap: a dark region between bands. The eye is drawn to bright walls, but the dark space between them is where price travels fastest.
- Volume profile: a thin book that persists produces a low volume node, since little trades where little rests.
In Senzoukria
On the heatmap screen the void is the dark area of the colour scale: the settings expose the scale and the DOM columns so the darkness can be read against the unit in use. The DOM ladder can show all levels or a chosen number of levels per side, and its help text notes that faded levels were seen earlier in the session and are no longer in the live book, which separates a void that just opened from one that was always there.
The guided tour describes the heatmap bands as liquidity waiting in the book; a void is the absence of those bands, and the app does not fill it with inferred size.
Common mistakes
- Treating a void as a target with a guaranteed fill. Slippage in thin conditions can be larger than the expected move.
- Reading thinness on a feed that delivers few depth levels: the book may be deep beyond what is displayed.
- Assuming thin means quiet. Thin books produce the largest moves per contract traded.
Related
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Frequently asked questions
- How thin is thin?
- There is no fixed number. Thinness is relative to the instrument's usual depth at that time of day and to the size you intend to trade. A level that absorbs a typical retail order in one session may be exhausted by the same order at the open of a holiday session. Compare cumulative depth with the same instrument's normal state.
- Why does price move so quickly through a liquidity void?
- Because each level in the void holds little size, a single market order can consume several levels in one fill. The price reported for each partial fill steps through the gap. Once the order reaches a level with real depth the move stops, which is why voids often end at a visible band.
- Does a thin book mean the market is about to reverse?
- No. It means the next moves will be disproportionate to the volume that causes them, in either direction. Direction depends on which side the aggression comes from and where depth is replenished. The book state tells you about sensitivity, not about direction.