What is an Order Book?
An order book is a real-time, continuously updated list of buy and sell orders for a trading pair, organized by price level. It displays the supply and demand at different prices, showing the depth of the market and the balance between buyers and sellers. Order books are the traditional mechanism for price discovery in financial markets.
Order Book Structure
An order book consists of two sides: bids representing buy orders and asks representing sell orders. The bid side shows orders from traders willing to buy, organized from highest to lowest price. The ask side shows orders from sellers, organized from lowest to highest price.
The best bid is the highest price someone is willing to pay. The best ask is the lowest price someone is willing to sell. The difference between these two prices is called the bid-ask spread.
Each price level shows the total quantity of orders at that price. This depth information reveals liquidity distribution and potential support and resistance levels where significant buying or selling interest exists.
Order Books in Crypto
Centralized exchanges like Binance and Coinbase use traditional order book models with matching engines that pair buyers and sellers. The order book approach allows for limit orders, providing precise price control for traders.
In DeFi, hybrid and on-chain order book DEXs have emerged. DYdX uses an off-chain order book with on-chain settlement. These systems aim to combine the benefits of order books with blockchain-based settlement and self-custody.
Reading Order Book Depth
Order book depth charts visualize cumulative buy and sell orders at each price level. The shape reveals market dynamics. A steep wall of buy orders below current price suggests strong support. Concentrated sell orders above indicate potential resistance. Imbalanced order books can signal potential price direction.
Order Book vs AMM Trading
Order books and AMMs represent fundamentally different trading mechanisms. Order books rely on limit orders from market makers and traders to provide liquidity. AMMs use liquidity pools and mathematical formulas to determine prices automatically.
Order books offer precise limit orders and potentially tighter spreads for liquid pairs. AMMs provide guaranteed liquidity and simpler user experience but may have higher price impact for large trades.