Order book

An order book is the real-time record of all open limit orders for a trading pair. Bids, the orders to buy, are listed from the highest price down, and asks, the orders to sell, from the lowest price up. The gap between the best bid and the best ask is the spread, and a matching engine pairs orders as soon as their prices cross.

Centralized exchanges such as Coinbase, Kraken and Binance run an order book for every market, and some on-chain venues such as dYdX and Hyperliquid do the same. Traders read the depth of the book to estimate how far a large order would move the price, and depth charts show walls of buy or sell interest.

An order book shows intentions, not commitments. Large orders can be placed and cancelled within seconds to create a false impression of demand, a practice known as spoofing, and thin books on small tokens can cause heavy slippage even on modest trades.