Technical Standards
A wide range of technical capabilities and disciplines impacting every aspect of electronic trading and the trade life-cycle.
FIX Trading Community activities span a wide range of technical capabilities and disciplines impacting every aspect of electronic trading and the trade life-cycle. This is the place to find the specifications and resources to help you effectively understand and use the various technical standards that make up the FIX Family of Standards.
Read our white paper on High Performance FIX for the Web Era, explaining how to use FIX and non-FIX technical standards with the FIX Protocol under different scenarios.
FIX Encoding Standards
FIX TagValue Encoding (ISO 3531 Part 1)
The FIX TagValue Encoding is the original and most widely used encoding for the FIX Protocol. It is a simple ASCII string format and became an ISO standard in 2022.
FIXML
FIXML is the XML encoding used within FIX. FIXML is widely adopted for derivatives post trade clearing and settlement globally.
SBE: Simple Binary Encoding (ISO/IEC 25390:2025)
Simple Binary Encoding is a high performance binary encoding in use within the industry for transactions and market data dissemination. Though initially created for and used within financial services, SBE is intended for general use and became an ISO/IEC standard in 2025.
FAST
FIX Adapted for Streaming is a protocol designed to reduce bandwidth use and latency for market data dissemination.
Guidelines For Using External Encodings
JSON
Encoding FIX using JSON is intended for both internal processing and the use of FIX within web based applications and APIs.
Google Protocol Buffers
Encoding FIX using Google Protocol Buffers is often used within companies as part of internal messaging.
ASN.1
Encoding FIX using Abstract Syntax Notation. ASN.1 is an ISO standard encoding system that includes multiple encodings itself.
FIX Session Standards
FIX Session Layer (Classic - ISO 3531 Part 2)
The FIX Protocol enables reliable, bidirectional communication between two parties through a session consisting of ordered messages with continuous sequence numbers, even across multiple connections.
Each FIX session features logon, message exchange—including resynchronisation if necessary—and logout, with interruptions possible due to transport, system, or application failures. The introduction of FIX Protocol Version 5.0 separated the session layer from the application layer, leading to the FIXT Session Profile, which now forms an integral part of the FIX Session Protocol.
FIXP - FIX Session Layer (High Performance)
The FIX Performance Session Layer (FIXP) is a “lightweight point-to-point protocol” introduced to provide an open industry standard for high performance computing requirements
FIX Session Layer (Message Framing)
The FIX Simple Open Framing Header (SOFH) standard solves the basic problem of knowing where one message ends and the next begins when messages are sent over a continuous data stream.
Instead of relying on special characters or assumptions about format, SOFH adds a small header in front of each message that clearly states its length and type.
This makes message handling simpler, more reliable, and better suited to modern, high‑performance systems, while allowing different message formats to be used over the same connection.
FIX Transport Standards
FIXS (FIX over TLS)
Transport Layer Security (TLS) is a widely used security standard that protects data as it moves between systems by encrypting the connection. FIXS is the standard to secure FIX sessions using this protocol.