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Polymarket uses a Central Limit Order Book (CLOB) for trading. Prices aren’t set by Polymarket—they emerge from supply and demand as users trade with each other.

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Prices Are Probabilities

Every share on Polymarket is priced between $0.00 and $1.00. The price directly represents the market’s belief in the probability of that outcome.
The displayed price is the midpoint of the bid-ask spread. If the spread is wider than $0.10, the last traded price is shown instead.

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Example

If the best bid for “Yes” is $0.34 and the best ask is $0.40:
You won’t necessarily trade at $0.37—you’ll pay the ask ($0.40) when buying or receive the bid ($0.34) when selling.

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The Order Book

The order book is a list of all open buy and sell orders for a market. It has two sides: The spread is the gap between the highest bid and lowest ask. Tighter spreads mean more liquid markets.

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Order Types

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Market Orders

Execute immediately at the best available price. Use when you want instant execution and are willing to pay the spread.
  • Buying: You pay the lowest ask price
  • Selling: You receive the highest bid price

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Limit Orders

Execute only at your specified price or better. Use when you want price control and are willing to wait.
  • Your order sits in the book until someone trades against it
  • Orders can partially fill as different traders match portions of your order
  • You can cancel unfilled orders at any time
All orders on Polymarket are technically limit orders. A “market order” is simply a limit order priced to execute immediately against resting orders.

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How Trades Work

Polymarket’s CLOB is hybrid-decentralized:
  1. Offchain matching — An operator matches compatible orders
  2. Onchain settlement — Matched trades settle via smart contracts
This design gives you the speed of centralized matching with the security of onchain settlement. You always maintain custody of your funds.

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Price Discovery

When a new market launches, there’s no initial price. The first price emerges when:
  1. Someone places a limit order to buy Yes at a price (e.g., $0.60)
  2. Someone places a limit order to buy No at the complementary price (e.g., $0.40)
  3. Since $0.60 + $0.40 = $1.00, the orders match
When matched, $1.00 is converted into 1 Yes token and 1 No token, each going to their respective buyers.

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Next Steps

Polymarket’s orderbook has no trading size limits — it matches willing buyers and sellers of any amount. However, large orders may move the price significantly. Always check orderbook depth before trading in size.

Positions & Tokens

Learn about outcome tokens and how positions work.

Order Lifecycle

Understand what happens from order placement to settlement.