What FIX is
FIX is a messaging standard rather than a single product. It defines a common format for the messages that financial systems exchange, covering both market data and order flow. Because many trading platforms implement it, FIX functions as a common protocol: two systems that both support FIX can connect without a bespoke integration for each pairing.
How a FIX session operates
FIX is session-based. Two parties establish a persistent connection, log on, and then exchange a stream of structured messages until the session ends, with the protocol keeping both sides synchronized. For market data specifically, a client requests the symbols it requires and then receives a snapshot followed by incremental updates as prices change, all within the same session.
FIX versus REST and WebSocket
REST and WebSocket are web transports, straightforward to adopt and well suited to modern applications. FIX originates in institutional trading and is the standard that order and execution systems use. A WebSocket feed and a FIX feed can carry the same prices; the difference is the protocol the receiving system uses. Organizations operating an existing trading stack often require FIX because their systems already support it.
Where FIX is used
FIX is used wherever professional trading systems connect: between a firm and its data providers, and between systems that place and manage orders. For market data, FIX delivers the same prices a REST or WebSocket client would receive, but into the session-based environment those systems already operate in, often with low-latency cross-connects in shared datacenters.
FIX on SiftingIO
SiftingIO offers market data over FIX 4.4 as an enterprise transport, market data only, across crypto, forex, and commodities. A client subscribes with a market data request and receives a snapshot followed by incremental refreshes within the session its trading systems already use, with low-latency cross-connects from SiftingIO datacenters. The data model matches the WebSocket and REST products, so prices are identical regardless of transport.