Version selection missing from



Does anyone here maintain the site? It looks like the FIX version selector has gone away and it is stuck on FIX.5.0SP2_EP247 - English.

Prior FIX versions via fiximate

Older versions are now considered legacy - the old site with the drop down is available here:


Thanks for asking that question.FIX Version 5.0 Service Pack 2 came out more than 10 years ago and is the last of the so-called “FIX legacy versions”. Since then, there have been many Extension Packs (see that provide incremental enhancements. There is now only one “version” of FIX which is called “FIX Latest” and is enhanced by means of Extension Packs. You can always agree bilaterally to use messages and fields from higher versions even if you use e.g. FIX 4.2.

The FIX Global Technical Committee has decided to always show FIX Latest when you go to There were a number of complaints that FIXimate would not show specific extensions. The reason was that people would use a personal bookmark and not go through the FIX website. If you need to go back to one of the legacy versions, there is a link on the top left side of FIXimate called “FIXimate for legacy versions”. The direct link is and it will give you the drop down box for versions.

We have just made the change a few days ago. Please clear out your browser cache.


Ah ok. I get that it is legacy from a version standpoint, but in terms of utilization pretty much everyone in the electronic trading space for stocks and options uses something in 4.1 - 4.4 versions (sometimes borrowing parts between versions) so it’s nice to be able look through those versions. It would be like shutting down all consumers using physical cables to connect to the internet because we’ve had wireless internet for 10+ years.

I’m glad the legacy site is still around, but please don’t remove it anytime soon. I don’t foresee anyone in the electronic trading space making migrations to FIX 5.x in the near future.


You are right in terms of FIX versions when it is about (US) equities or equity options and trading between buy-side and sell-side, using tag=value syntax. FIX now supports basically all asset classes and FIX generation 5 is offered quite a bit around the world, especially by exchanges and clearinghouses. This may also be tag=value encoding but often it is FIXML or one of the binary FIX encodings (e.g. SBE). There may also be a different session layer (e.g. Websphere MQ or AMQP) in place. FIX generation 4 is about a monolithic approach for the three layer (application, presentation aka encoding, session). FIX generation 5 did not change the concepts of the application layer but gave a choice for the other two layers (to be fair, FIXML was already offered with FIX 4.4). This allows to transport FIX messages in multiple ways, not just between the classic FIX engines.

The FIX version is most important between FIX 4.2 and FIX 4.4 because of concept changes that were made back then and that FIX would no longer make these days to avoid breakage of existing applications. You can rest assured that FIX will continue to support the following application level versions (see also

  • FIX 4.2
  • FIX 4.4
  • FIX 5.0 SP2

These are the major legacy versions that are still in use. Legacy versions can be enhanced by using tags from higher versions (basically FIX Latest). This is apparently an issue for some of the FIX 4.2 users. In case of regulatory requirements, FIX has accommodated FIX 4.2 users by creating user-defined fields in the 8000 - 8499 range in addition to new tags in the standard 1 - 4999 range.

See for officially unsupported FIX legacy versions. This only means that FIX encourages users to migrate to FIX Latest or one of the supported legacy versions if the former is not possible.

As far as your example is concerned, I do not see wireless as another “version” for connecting to the internet. The situation is rather similar to asking Microsoft to support Windows XP or Word 95 to run a PC or write a document. Nobody expects these legacy software versions to be supported indefinitely. FIX as a specification written on paper is a little different from a piece of software, hence FIX continues to provide workarounds for FIX 4.2 which was published almost 20 years ago!