🆓 Free 30-Day Trial — No Credit Card

Free Modbus Simulator for Windows

Full-featured Modbus simulator — TCP, RTU, ASCII, Master mode, Slave mode — completely free for 30 days. No registration. No credit card. Download in 30 seconds.

⬇ Download Free — v1.2.7 (Windows)

30 days · All features included · No watermarks · Windows 10/11

Everything Is Free for 30 Days

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Modbus TCP Slave — simulate any TCP/IP slave device on port 502

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Modbus RTU Slave — RS-485, RS-232, or virtual COM port

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Modbus ASCII Mode — full ASCII framing support

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Modbus TCP Master — poll any TCP slave device

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Modbus RTU Master — poll RTU devices over serial port

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8 simultaneous slaves — simulate full device networks

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All function codes — FC01 through FC16

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32-bit float / INT32 — all data types, all byte orders

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CSV register import — load device register maps instantly

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Transaction log — every frame logged with timestamps

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Exception simulation — test error handling in master apps

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Save/load configs — reuse slave configurations across sessions

After 30 Days

After the free trial, you can purchase a one-time license for $59. That includes Master mode, Slave mode, all protocols (TCP, RTU, ASCII, UDP), and all future version updates. No subscription. No annual fee. See how that compares to a Modbus Poll license.

Other tools (separate)

$130+

Modbus Poll + Modbus Slave

ModbusSimulator.com

$59

Master + Slave, all protocols

Start Free Trial →

Other Free Modbus Tools — How They Compare

There are several free Modbus tools available. Here's how they compare to the ModbusSimulator.com free trial:

QModMaster — Free, master-only, no slave simulation. Good for basic TCP/RTU master testing.
ModRSsim2 — Free but abandoned (~2014). RTU slave only. Windows 10/11 compatibility issues.
ModbusPal — Free, Java-based slave simulator. Last updated 2015. No active development.
diagslave — Free CLI slave. No GUI. Good for CI/CD automation only.
pymodbus — Free Python library. Requires programming. Most powerful but no GUI.
ModbusSimulator.com trial — Free for 30 days. Master + Slave, TCP + RTU, GUI, Windows 11, actively maintained.

→ See full comparison table of free Modbus simulators

FAQ

Is the free trial really free — no credit card?

Yes. The 30-day trial requires no registration, no email address, and no credit card. Download the installer, run it, and the full application opens. After 30 days, a license screen appears. You can purchase a $59 license to continue, or stop using it. No charges, no automatic renewals.

What happens after the 30-day trial?

The application continues to work in a limited mode — you can still view saved configurations. To use the simulator for active sessions, you purchase a one-time $59 license. There are no subscription fees and the license never expires.

Is there a free version with permanent limited features?

The current model is a 30-day full-featured trial followed by a paid license. There is no permanently free limited version. For a free alternative with permanent access, QModMaster (master only) or diagslave (slave, CLI only) are open-source options.

Does the free trial include Modbus RTU?

Yes. The trial includes all protocols: Modbus TCP/IP, Modbus RTU (serial), and Modbus ASCII. For RTU testing without RS-485 hardware, use com0com (free) to create a virtual COM port pair on the same PC.

Download Your Free Modbus Simulator

30 days · All features · No registration · Windows 10/11

⬇ Download Free — v1.2.7

After 30 days: $59 one-time license. No subscription. See pricing →