FIX Protocol Trading

FIX (Financial Information eXchange) is the industry standard protocol for electronic communication of securities trading orders and market information. It's binary, compact, and optimized for sub-millisecond latency. Every stock trade you make (directly or indirectly) passes through FIX. FIX messages contain order data (buy/sell, symbol, quantity, price, timing), execution reports (accepted, filled, rejected), and market data. The protocol is agnostic to transport (TCP, multicast, carrier pigeon in theory), but latency-conscious firms optimize ruthlessly: FIX over dedicated fiber = microseconds of latency.