The FIX Protocol
A global and open standard that enables fast, secure and accurate exchange of trading information, reducing complexity, lowering costs and improving reliability across financial markets.
An Introduction to the FIX Protocol
The FIX Protocol is a global, open standard that enables financial institutions to communicate trading information quickly, accurately and securely.
It provides a common “language” that allows firms such as banks, asset managers, exchanges and technology providers to connect and exchange information without needing bespoke connections for each counterparty.
By using a shared standard, the industry reduces cost, complexity and operational risk, while improving speed and reliability. Developed and maintained by the FIX Trading Community, the FIX Protocol has evolved over more than three decades to support a wide range of asset classes and market activities.
Its open, vendor‑neutral nature encourages broad adoption and collaboration, helping firms adapt to new market practices, regulatory requirements and technologies while maintaining efficient and resilient financial markets.
What It Is (and Isn't)
The FIX Protocol is an application‑layer protocol, meaning it defines what business information is being exchanged and what it means, rather than how that information is physically sent across a network.
In practical terms, FIX specifies the structure, content and workflows of trading messages—such as orders, executions and market data—while deliberately remaining independent of any particular network, transport or technology stack.
This separation allows the same FIX business messages to be carried over different transports (for example TCP/IP, multicast or WebSockets), managed using different session models, and encoded in different formats (such as traditional tag‑value, binary or JSON), depending on performance, resilience or integration needs.
As a result, FIX can be adapted to a wide range of use cases—from ultra‑low‑latency trading to web‑based and cloud‑native environments—without changing the underlying business meaning of the messages.
How It Works
The FIX Protocol is structured in a layered, modular way to promote reuse, consistency and clarity.
At its core are fields, each identified by a numeric tag and a defined meaning (such as price, quantity or instrument), which form the basic building blocks of all FIX data.
Related fields are grouped into components, which represent logical business concepts (for example, parties, instrument details or allocations) and can be reused across many messages.
Messages are then constructed by combining fields and components to represent specific business events or actions, such as submitting an order, reporting an execution or publishing market data.
Messages are organised into categories (for example, order handling, market data, trade reporting or post‑trade processing), which group related message types and workflows.
This structured approach allows FIX to be both highly standardised and extensible, supporting consistent interpretation while accommodating different asset classes and use cases.
The FIX Protocol initially grew through a series of distinct releases. Since 2019 (HANNO TO CHECK), the protocol ("FIX Latest") is now upgraded incrementally through extension packs.
These are backwards compatible and can even be used on legacy versions of the protocol.
How It Evolves
The FIX Protocol is developed through a structured, industry‑driven process that begins with business requirements identified by market participants in FIX working groups.
These groups—made up of buy‑side, sell‑side, venues, vendors and other stakeholders—define the business problem and agree the required workflows and data in plain business terms, which are documented in a formal gap analysis.
This proposal is then translated into detailed technical specifications by FIX's technical standards group and reviewed by FIX's Global Technical Committee to ensure consistency, quality and alignment with existing standards.
The specification then goes through a two to four week public review before being incorporated into the standard.
Specifications
FIX Latest
FIXimate - the easiest way to navigate the full FIX Protocol specification
FIX versions 4.2 and 4.4 are still supported by the FIX Trading Community. The other versions are no longer supported but are available in our archive.
FIX Latest Specification - Introduction 5.6 MB 3781 downloads
Introduction to FIX Latest and layouts of global components. ...
FIX Latest Specification - Infrastructure 743 KB 2073 downloads
Normative specification of the infrastructure business area of FIX Latest. ...
FIX Latest Specification - Pre-Trade 5.4 MB 2439 downloads
Normative specification of the pre-trade business area of FIX Latest. ...
FIX Latest Specification - Trade 3.2 MB 3990 downloads
Normative specification of the trade business area of FIX Latest. ...
FIX Latest Specification - Order State Changes 1.2 MB 3042 downloads
Normative specification of the order state changes of FIX Latest. ...
FIX Latest Specification - Post-Trade 4.7 MB 2366 downloads
Normative specification of the post-trade business area of FIX Latest. ...
Time Precision Technical Addendum 580.93 KB 5928 downloads
Time Precision Technical Addendum. This Technical Addendum addresses the time precision...External Codelist
Extraordinary_Event_Type 331.09 KB 428 downloads
The ExtraordinaryEventType enumerations are used by the following fields: ExtraordinaryEventType(42297) LegExtraordinaryEventType(42389) UnderlyingExtraordinaryEventType(42885) ...
Deliverable Obligation Type 144.04 KB 453 downloads
The DeliverableObligationType code list is used by the following field: PhysicalSettlDeliverableObligationType(40210) ...
Credit Event Type 291.73 KB 283 downloads
The CreditEventType code list is used by the following fields: ComplexEventCreditEventType(40998) LegComplexEventCreditEventType(41367) UnderlyingComplexEventCreditEventType(41717) ...
PayDisputeReason 162.30 KB 310 downloads
The PayDisputeReason code list is used by the field PayDisputeReason(2800). ...
Asset Type 303.04 KB 858 downloads
The AssetType enumerations are used by the following fields: AssetType(1940) SecondaryAssetType(1979) LegAssetType(2069) LegSecondaryAssetType(2079) UnderlyingAssetType(2015) UnderlyingSecondaryAssetType(2083) ...Legacy Versions
The following FIX Latest specifications are complete up to extension pack 284, and should be read in conjunction with later extension packs for features added in those packs.
FIX 4.2 Specification with Errata 20010501 1.34 MB 4545 downloads
FIX 4.2 Specification with May 1, 2001 Errata. ...