Order book
Polymarket and Kalshi both show live order books for each market.
Prediction Markets 101 editorial team Updated April 16, 2026 1 min read
Definition
An order book is the full list of all active buy and sell orders at various prices for a given market.
Plain-English explanation
The top of the book is the best bid and best ask — the prices at which an instant trade would happen. Levels below show orders at worse prices. Depth = how much size is at each level.