FIXSIM User Guide

FIXSIM is a browser-based FIX Protocol testing and simulation platform used by QA engineers, developers, and integration teams at broker-dealers, OMS/EMS vendors, buy-side firms, and fintech companies worldwide.

Whether you are developing a new Order Management System (OMS) or Execution Management System (EMS), integrating with a broker-dealer, or certifying an exchange API, FIXSIM provides a high-performance FIX testing environment accessible entirely from your browser — no local installations required.

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What You'll Find in This Guide

• Getting Started — Connect your FIX engine to FIXSIM for the first time.
• FIX Sessions — Create and manage FIX initiator and acceptor sessions.
• Configuring Sessions — Mirror your production FIX session settings.
• Sending & Receiving Messages — Send FIX flows and inspect FIXSIM responses.
• Session Views — Monitor real-time message flows and session state.
• Reports Overview — Understand FIXSIM reporting and blotter views.
• Blotter In — View inbound orders and executions.
• Blotter Out — View outbound orders and execution reports.
• Custom Tags — Configure and apply custom FIX tags to your sessions.
• FIX Session Settings — Detailed session configuration reference.
• App Settings — Manage application-level settings and preferences.
• Log Replay — Upload and replay FIX log files, view replay stats, and download session logs.
• Rules & Automation — Build automated FIX test scenarios with the Rule Builder.
• REST API — Drive sessions, orders, executions, and raw message injection programmatically.
• Troubleshooting — Resolve common FIX connection and sequence issues.
• Reference — Links to FIX tutorials, sample messages, and glossary.

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New to FIXSIM?

Start with the Getting Started guide to connect your first FIX session. For a broader introduction to FIX protocol testing, see What is a FIX Simulator or explore the FIX Protocol Resources library.