Order Book
The live list of all resting bid and ask limit orders for a market, organized by price level.
Definition
An order book is the real-time record of all outstanding limit orders in a market, split into bids (buyers willing to pay up to a certain price) and asks (sellers willing to accept at least a certain price). Orders are sorted by price priority and, within a price level, by time priority. The order book is the core data structure of a Central Limit Order Book (CLOB).
In practice
Polymarket exposes the live order book for any outcome token via its CLOB API. A bot can fetch the best bid, best ask, and full depth at each price level. A depth check before entry reveals whether sufficient size exists to fill the intended order without significant slippage. Poly5m-v3's maker phase monitors the book continuously: if the bot's resting GTC order falls outside the top-3 price levels due to new competing quotes, it cancels and reposts closer to the mid-price to maintain fill priority.