Crypto glossary
Order book DEX (CLOB)
An order book DEX matches buy and sell limit orders in a central limit order book (CLOB), fully on-chain or with off-chain matching, instead of an AMM.
Most early DEXs used automated market makers because Ethereum was too slow and expensive to update an order book on every trade. Order book DEXs bring back the familiar model of exchanges: traders post limit orders at chosen prices, a matching engine pairs them, and the book shows depth at every level. Some run everything on-chain, which high-throughput chains such as Solana, Sei or dedicated app-chains make feasible; others match off-chain and settle on-chain.
The model suits professional market makers, offers tighter spreads on liquid pairs and supports advanced order types. It dominates on-chain perpetual futures, with venues such as Hyperliquid and dYdX built around a central limit order book, and it is used for spot trading by projects like OpenBook and Phoenix.
Order books need active market makers; without them, books are thin and prices jump. Hybrid designs reintroduce trust in the operator that runs matching, which can censor or reorder orders. Fully on-chain books are exposed to front-running and depend on fast, cheap block space.
Example
A trader places a limit order to buy SOL 2% below the market on an on-chain order book DEX; when price dips, the order is matched against a market maker's sell order and settles in the same block.