FIXSIM
FIX Simulator for Development, QA, and Regression Testing
Connect your FIX engine to FIXSIM and simulate real trading workflows: logons, sequencing, resends, orders, fills, cancels, rejects, and replaces. Test manually in the portal or automate using rules and REST APIs.
- Web-based (no installs)
- Manual + automated testing
- Rule-driven counterparty behavior
- Custom tags + dictionaries
- High-volume simulation ready
- Month-to-month pricing
Web-based FIX simulator for fast, repeatable testing.
Who Uses a FIX Simulator
Development
Build and validate integrations while implementing new flows.
Quality Assurance
Run repeatable regression tests and edge case scenarios.
Support
Reproduce production issues by replaying message behavior.
Sales / Demos
Demonstrate real-world workflows with controlled outcomes.
Why Teams Choose FIXSIM
What is a FIX Simulator?
The FIX protocol is an open and free specification maintained by the FIX Trading Community. Since 1992, it has enabled the securities trading industry to exchange orders, executions, and other financial messaging between trading systems.
If you are building your own trading system (or integrating with a vendor’s solution), having a reliable testing and development environment is crucial. A FIX Simulator provides the counterparty side of trading so you can validate behavior before production.
Buy Side Use Case
Simulate a broker/dealer destination to route orders for execution. Control outcomes such as order rejections, acknowledgements, partial fills, cancel/corrects, done-for-day, and more.
Sell Side Use Case
Simulate client order flow into your service. Create multiple connections, submit orders, initiate cancels, and initiate modification requests to validate production readiness.
Why do I need a FIX Simulator?
A robust FIX simulator provides reliable testing to ensure your trading system can handle not only standard workflows, but also integration requirements like FIX customizations, reliable message delivery, resequencing for recovery, and high volumes of messaging.
A simulator isn’t just for initial development. It remains valuable as your system expands, scales, and grows in scope.
FIX Simulator Options
There are a few ways to implement a FIX testing environment.
Build your own
Building your own FIX simulator is a costly expenditure for most firms. It becomes another internal software project to maintain, requiring expertise and continued engineering effort.
Using a broker/dealer test environment
A trading partner may provide access to a test environment, but it’s often limited to one vendor’s workflows and availability. Many teams also find reliability inconsistent and manual coordination required.
Using a vendor solution (FIXSIM)
A vendor solution like FIXSIM provides years of expertise and scalable testing. As a SaaS solution, there is no hardware to maintain. Connect your FIX-enabled application and use the web portal to configure, monitor, and take action on your trading workflows.
The Power and Flexibility of FIXSIM
Hosted Solution
Nothing to download, install, or maintain. Connect your FIX engine and test from anywhere with on-demand access.
Customizations
Support custom tags/values and upload custom QuickFIX data dictionaries for any session.
Manual User Workflows
Configure FIX sessions, set default behaviors, and take action on trades including acknowledgements, rejections, partial executions, status updates, cancellations, and more. Recreate issues by replaying messages.
Automated Testing
Configure rules to automate workflows (e.g., reject trades > 5000 shares or partial fill NVDA orders). Use OpenAPI/Swagger to control FIXSIM from your application or CLI in your preferred language.
Summary
FIXSIM was created from real-world FIX protocol development, integration, and support experience. Originally built for Gamma Three Trading to test and validate trading infrastructure, FIXSIM is both our product and a tool we rely on ourselves.
On-demand FIX Simulator
Try FIXSIM and start testing in minutes.
"We started with our UK QA team, now rolled out to global teams!"
"Essential to help us stress test clients accessing our Dark Pool"
"As a contractor, I use FIXSIM for helping build FIX solutions for my clients."
