Quick definition FIX is a universal, standardised electronic protocol used by brokers and traders to exchange orders and execution information. It is venue-agnostic and works across exchanges, brokers, and trading platforms. What it is FIX is a text-based protocol (unlike the binary ITCH and OUCH). A FIX message looks like: 8=FIX.4.2|9=40|35=D|49=TRADER|56=BROKER|34=1|52=20240101-12:30:00|... Each pipe-separated field carries information. The message type (35=D) means "New Order Single". Why it matters FIX is the industry standard for order routing and execution reporting. Nearly every broker and venue supports FIX. A trading system can use FIX to connect to multiple brokers and venues without custom integration for each. FIX is slower than venue-native protocols (OUCH, ITCH) but is more universal. FIX versions and fields FIX has multiple versions (4.0, 4.2, 4.4, 5.0). Newer versions add fields and functionality. Most brokers support FIX 4.2 or 4.4. FIX messages include fields for: - Order details (symbol, price, size, side) - Account information - Execution details (fill price, fill size) - Timestamps Practical example A hedge fund uses FIX to route orders through multiple brokers. They send a FIX "New Order Single" message to Broker A for 10,000 shares of Apple. Broker A responds with a FIX "Execution Report" showing the order has been accepted. Later, the order partially fills. Broker A sends another FIX "Execution Report" showing 5,000 shares filled at 150.00. FIX versus OUCH OUCH is NASDAQ's native protocol; FIX is universal. OUCH is faster (lower latency) but works only with NASDAQ. FIX is slower but works everywhere. Professional traders often use both: OUCH for NASDAQ and FIX for everything else. See also - OUCH (Order Unwind and Clearing House) - ITCH (Interactive Transparent Clearing House) - Order Submission - Execution Reporting
