FIX Protocol Simulator for Capital Markets Testing
Compose FIX messages in plain English. Test order routing, execution reports, and auto-response scenarios — without waiting for exchange access.
Download Free Trial | Features | Pricing | Website
MockFIX is a desktop FIX protocol simulator purpose-built for capital markets BAs, QA teams, and developers who need to test FIX 4.4 order flows without live exchange access.
Instead of spending weeks setting up QuickFIX, writing custom scripts, or waiting for UAT environments, MockFIX lets you create a FIX session, send a message, and see the response in under 5 minutes.
- QA Engineers testing OMS integrations (Fidessa, Bloomberg, FlexTrade, Charles River)
- Business Analysts validating order workflows and execution report flows
- Developers building FIX clients who need a mock counterparty
- Support Teams debugging FIX message issues in production
Create and manage multiple FIX 4.4 sessions with full control over connection settings. Run in simulated mode (offline, no server needed) or TCP initiator mode (connect to a real FIX acceptor).
Describe your order in natural language and the AI composes the correct FIX message with all the right tags and values. No tag memorisation required.
Examples:
"Buy 1000 AAPL at 150 limit, day order"→ Correct NewOrderSingle (35=D) with Side=1, OrdType=2, TimeInForce=0"Explain this execution report"→ Tag-by-tag breakdown in plain English"Reject all orders for symbol TEST"→ Auto-response rule created
Real-time order tracking across all sessions. Filter by status, search by ClOrdID, and drill into the full FIX message trail for any order.
Start with built-in templates for common FIX message types — NewOrderSingle, Cancel Request, Cancel/Replace, Execution Report. Create and save custom templates for repetitive testing.
Paste two FIX messages side by side and compare them field by field. Differences are highlighted instantly — useful for debugging rejects or verifying amend changes.
Configure automatic responses to incoming FIX orders: acknowledge, fill, partial fill, reject — with conditional logic based on symbol, side, order type, or any FIX tag value.
Deploy the Execution Engine as a standalone server so your entire team connects to the same mock exchange.
Build multi-step automated test flows: send an order, expect an execution report, amend, cancel — then run the entire scenario with one click.
Import FIX log files from production or UAT (QuickFIX, pipe-delimited, SOH-delimited formats). Browse parsed messages and replay them into a live session.
| Message Type | Tag 35 | Description |
|---|---|---|
| NewOrderSingle | D | Submit a new order |
| OrderCancelRequest | F | Cancel an existing order |
| OrderCancelReplaceRequest | G | Amend an existing order |
| ExecutionReport | 8 | Order status and fill updates |
| OrderCancelReject | 9 | Rejection of cancel/replace |
| Logon | A | Session authentication |
| Heartbeat | 0 | Session keepalive |
| ResendRequest | 2 | Sequence gap recovery |
| MockFIX | Build Your Own | |
|---|---|---|
| Time to first test | 5 minutes | 2-4 weeks |
| GUI for non-developers | Full desktop app with visual editor | Usually CLI-only |
| AI message composition | Built-in — plain English to FIX | None |
| FIX session management | Built-in logon, heartbeat, sequence numbers | Must implement yourself |
| Auto-response rules | Configurable, no code | Custom code for every scenario |
| Template library | Pre-built + custom templates | Build your own catalog |
| Team sharing | Deploy engine server, whole team connects | Build multi-user support |
| Maintenance | Updates delivered automatically | You own every bug |
- OS: Windows 10 or 11 (64-bit)
- RAM: 4 GB minimum
- Disk: 500 MB available
- Network: Internet for sign-in and AI features
- Download — Get MockFIX (free 14-day trial, no credit card)
- Extract — Unzip to any folder, double-click
MockFIX.exe - Create account — Sign up when the app launches (or sign in if you have an account)
- Create a session — Go to FIX Sim → New Session → Choose Simulated mode
- Send a message — Pick a template or use the AI assistant:
"Buy 500 MSFT at 420 limit"
The MockFIX Execution Engine can run as a standalone server for team-wide testing:
# Docker
docker pull mockfix/engine-server:latest
docker run -p 8090:8090 -p 9880:9880 mockfix/engine-server
# Or download the standalone package
# https://mockfix.com/download (Pro + Engine plan)The engine server accepts incoming FIX connections and responds based on your configured auto-response rules.
- FIX Protocol Guide — Introduction to FIX for beginners
- FIX Tag Reference — Searchable FIX 4.4 tag database
- Sample FIX Messages — Common FIX message examples
- Blog — FIX testing tutorials and best practices
| Plan | Price | Includes |
|---|---|---|
| Starter | $49/mo | FIX Simulator, Templates, Message Diff |
| Professional | $99/mo | + AI Assistant, Test Scenarios, Log Replay |
| Pro + Engine | $199/mo | + Execution Engine, Server Deployment |
All plans include a 14-day free trial with full access. No credit card required.
- Website: mockfix.com
- Download: mockfix.com/download
- Contact: admin@mockfix.com
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