Methods, systems, and computer-readable media for providing a rule based exchange simulator are presented. A plurality of rules may be received at an exchange simulator that define how orders should be processed at the exchange simulator. The received rules may be stored, for instance, at a rules engine. For example, rules may comprise a fill rule, a cancel rule, a reject rule, a no acknowledgment rule, and a market data rule. An order that comprises a stock exchange order may be received at the exchange simulator. For example, an order may comprise a buy or sell order for a particular instrument, such as a stock, and may comprise a particular quantity. Based on the one or more rules stored in the rules engine, the received order may be fully filled, partially filled, or not filled.