Quick answer
An order book lists open buy and sell orders for an asset at different prices.
What is Order book?
An order book is a live queue of bids from buyers and asks from sellers. Its visible depth can help explain spread and execution, but it can change quickly and may not show hidden or off-platform liquidity.
The useful way to approach this term is to separate its definition from the assumptions people often attach to it. In crypto, the same word can appear in a protocol rule, a user interface, a market-data label, or a marketing claim. Check which layer the explanation is describing.
Why does order book matter?
Order-book depth affects the likely execution price of a trade. Thin depth can make a seemingly small market order move the price more than expected.
Concrete example
See it in a real situation
If the lowest ask is $100 and the next asks are $100.20 and $100.60, a large buy may fill across several levels instead of receiving one price.
Common misconceptions
What this term does not mean
- Displayed orders are not guaranteed to remain until your trade reaches them.
- An order book does not show every source of liquidity in the market.
Related terms
Sources and further reading
Definitions are written for education and checked against the sources below where relevant. A source can explain a protocol or rule without endorsing every product built around it.