A list of all pending buy and sell orders at different prices. Platforms with order books offer better price transparency.
An order book displays all pending buy and sell orders for an event contract at each price level. It shows market depth — how many contracts are available at each price — and the bid-ask spread.
Platforms with order books (Kalshi, Polymarket, ForecastEx, PredictIt) allow limit orders, where you set your price and wait for a match. Platforms without order books (Robinhood, DraftKings, FanDuel) fill orders at the current market price.
Order book depth matters for large positions. Thin markets mean more slippage — the difference between your expected price and what you actually pay.
An exchange where participants trade contracts based on the outcome of future events, with prices reflecting collective probability estimates.
SlippageThe difference between the expected price and the actual execution price, usually caused by thin liquidity or large order sizes.
LiquidityHow easily you can buy or sell contracts without significantly moving the price. More liquidity means tighter spreads and less slippage.