An order book is a digital ledger used by cryptocurrency exchanges to display all active buy and sell orders for a trading pair. It provides a real-time view of market supply and demand, showing the prices at which traders are willing to buy (bids) and sell (asks) an asset.
The order book is divided into two sides:
- Bid side (buy orders) — lists all pending buy orders from highest to lowest price, showing how much buyers are willing to pay
- Ask side (sell orders) — lists all pending sell orders from lowest to highest price, showing the minimum sellers will accept
The gap between the highest bid and lowest ask is called the spread. A narrow spread typically indicates high liquidity, while a wide spread suggests lower liquidity and potentially higher slippage.
Traders use order book data to:
- Gauge market depth — see how much liquidity is available at each price level
- Identify support and resistance — large clusters of orders can indicate key price levels
- Place strategic orders — position limit orders at favorable price points
- Detect market manipulation — spot suspicious patterns like spoofing or wash trading
Order books are the foundation of centralized exchanges like Binance, Coinbase, and Kraken. In contrast, most decentralized exchanges use an automated market maker (AMM) model instead of order books, though some newer DEXs are combining both approaches.
Understanding order book dynamics is essential for any trader looking to move beyond basic market orders and develop more sophisticated trading strategies.