Orderbook

An orderbook is a real-time list of all outstanding buy and sell orders for a prediction market contract, organized by price level. It shows the supply and demand at every price point.

CLI:sf depth KXCPI-26MAR-T3.5

Reading an Orderbook

The orderbook is the most important data structure in trading. It shows you exactly who wants to buy and sell, and at what prices.

Structure

An orderbook has two sides:

Bids (left/buy side): Orders from people wanting to buy. Sorted highest price first. The best bid is the highest price anyone will pay.
Asks (right/sell side): Orders from people wanting to sell. Sorted lowest price first. The best ask is the lowest price anyone will accept.

What It Tells You

Current price: The midpoint between best bid and best ask
Spread: The gap between best bid and best ask
Depth: How many contracts are available at each price level
Support/resistance: Large resting orders act as barriers to price movement
Imbalance: If bids are much larger than asks (or vice versa), it suggests directional pressure

Orderbook vs. AMM

Kalshi uses an orderbook model where every trade matches a specific buyer with a specific seller. Polymarket uses an AMM (Automated Market Maker) for most markets, where you trade against a liquidity pool rather than specific counterparties. The CLI normalizes both into a consistent format.

Using the Orderbook for Edge Detection

The orderbook reveals more than just prices. A thin orderbook with a big ask wall at 35 cents might indicate a large seller who needs to exit — potentially creating an opportunity if your thesis says fair value is higher.

Example

sf depth KXCPI-26MAR-T3.5:

  BIDS                    ASKS
  ----                    ----
  200 @ $0.50             100 @ $0.53
  400 @ $0.49             250 @ $0.54
  150 @ $0.48             500 @ $0.55  ← ask wall
  600 @ $0.47             100 @ $0.56

Best bid: $0.50  |  Best ask: $0.53
Spread: $0.03    |  Midpoint: $0.515

The 500-contract ask wall at $0.55 suggests a large
seller is defending that level. To push the price above
$0.55, buyers would need to absorb 850 contracts.

Related Terms

Market Maker

A market maker is a participant who continuously provides both buy (bid) and sell (ask) orders on a prediction market, earning the spread in exchange for providing liquidity to other traders.

Bid-Ask Spread

The bid-ask spread is the difference between the highest price a buyer will pay (bid) and the lowest price a seller will accept (ask). It represents the cost of trading immediately.

Bid and Ask Prices

The bid price is the highest price a buyer is currently willing to pay for a contract. The ask price is the lowest price a seller is currently willing to accept. Together they define the tradeable price range.

Market Depth

Market depth is the total quantity of resting orders at each price level in the orderbook. Deep markets can absorb large trades with minimal price impact; shallow markets cannot.

Liquidity

Liquidity is the ease with which you can buy or sell a prediction market contract without significantly affecting its price. Liquid markets have tight spreads, deep orderbooks, and high trading volume.

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