# Order Book

> A live list of buy and sell orders at different prices on an exchange.

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Source: What The Block! Dictionary v1.0 (last updated 2026-04-25), browsable at https://wtb.fudfomo.co.

## Definition

An order book is the central data structure on a traditional exchange. It shows every outstanding buy and sell order, sorted by price, and updates in real time as new orders arrive and existing ones are filled or cancelled.

Centralised crypto exchanges use order books, and so do a small number of on-chain DEXes. The depth of the book at each price level is a basic measure of how much you can trade without moving the price.

## Related terms

- [CEX](https://fudfomo.co/glossary/cex): A centralised exchange. A regulated platform where you buy and sell crypto using an account.
- [DEX](https://fudfomo.co/glossary/dex): A decentralised exchange. Trade crypto directly from your wallet, without an account.
- [Market Maker](https://fudfomo.co/glossary/market-maker): A participant who quotes both buy and sell prices, providing liquidity in exchange for a small spread.
- [Slippage](https://fudfomo.co/glossary/slippage): The gap between the price you expected when you placed a trade and the price you actually got.

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