System

Polymarket's Order Book, or CLOB (Central Limit Order Book), is hybrid-decentralized. It includes an operator for off-chain matching/ordering, with settlement executed on-chain, non-custodially, via signed order messages.

The exchange uses a custom Exchange contract facilitating atomic swaps between binary Outcome Tokens (CTF ERC1155 assets and ERC20 PToken assets) and collateral assets (ERC20), following signed limit orders. Designed for binary markets, the contract enables complementary tokens to match across a unified order book.

Orders are EIP712-signed structured data. Matched orders have one maker and one or more takers, with price improvements benefiting the taker. The operator handles off-chain order management and submits matched trades to the blockchain for on-chain execution.