FIX messages

In other posts in this series, I’ve introduced some of the key concepts of the FIX protocol, as well as some of the history. In this article, I’d like to dive into the basics of how the protocol itself works.

What is a FIX Engine? Where Does It Sit?

First of all, we need to talk about an important piece of software called a FIX engine. Each party would have one or more trading applications, which would interface to a FIX engine, which in turn connects over a network to others. So you can think of a FIX engine as the computer component that is the real interface between…


In this article, I’d like to shine a light on an area of FIX that seems to be quite confused in people’s minds, and that is the “security” (or not) of FIX specifications.

Current Perspectives

The background to this is that we conducted some market research in December 2020 in which we asked people how they distribute their FIX specifications today. We found that 51% of respondents said that they

email a PDF to a defined distribution list, and a further 24% said that they simply post a PDF onto their website. So we can simply conclude then that the vast majority…


If you are interested in financial markets, then you may have come across references to the FIX (Financial Information eXchange) protocol. So what is it, and why is it so important?

Let’s start with a bit of history.

London Stock Exchange trading floor before Big Bang (Source: The Times)

27 October 1986 was a pivotal day in the history of the UK; a day known as “Big Bang”. It is a day that saw massive, sweeping deregulation of the way that financial markets operated that forever changed the way stocks and shares were traded; away from the ‘in-person’ trading on the floor of the London Stock Exchange, towards electronic and phone-based…


One of the trends that we are seeing with more recent trading venues (which tend to be crypto exchanges), is that they are starting to offer both REST/Websocket and FIX interfaces. You might be asking why have both, and what’s the difference between them?

I’ll assume here that if you are reading this, you know probably know more about REST/Websocket APIs than FIX APIs because it’s quite an old and specialist protocol.

FIX was originally launched in the early 90s (a time before the modern internet!) and has grown to dominate institutional market connectivity within trading; it’s the protocol that…


I write this on 23rd September 2019, the day of UN Climate Action Summit.

In recent days and weeks, we’ve seen worldwide protests as millions take to the streets to demand action to tackle climate change. Will it fall on deaf ears? Unfortunately it may. And that’s not good enough.

The facts about climate change that we already see are scary. The predictions about the future are horrific. Perhaps some people can justify their inaction by thinking that 2050 seems a really long time away, or that one person changing their behavior can’t possibly make a difference. …

Chris Lees

Founder @ FixSpec. One man, trying to make a difference.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store