August 11, 2026 · Comparison

Modbus Poll vs Modscan vs Modbus Slave: Which Master Tool to Use

You need to read holding register 40001 from a power meter, or write a setpoint to a VFD, and you need a Modbus master tool to do it. Search for one and the same three names come up everywhere: Modbus Poll, Modscan, and a handful of Modbus Slave simulators. The names are confusingly similar, the screenshots look interchangeable, and nobody explains which one you actually want.

This guide compares the three on the dimensions that matter: what platform they run on, whether they do TCP and RTU, whether they can only poll or also simulate a slave, and what they cost. If you want the deeper protocol background first, see our Modbus protocol primer or the function code reference.

The Three Tools, in One Sentence Each

• Modbus Poll (Witte Software) — the de facto Windows Modbus master. Mature, actively updated, multi-document interface, paid license. Windows only.
• Modscan / Modscan32 — a legacy free Windows utility. Functional for quick reads, but the UI is from another decade and development stopped years ago.
• Modbus Slave (Witte Software) — the companion to Modbus Poll. Same vendor, same look, runs as a slave/server simulator so a master has something to talk to. Windows only.

Notice the pattern: every one of these is a Windows application. If you are on macOS or Linux, none of them runs natively. That single fact drives most of the "which tool should I use" decisions in the field. More on the Mac gap below.

Feature Comparison

Modbus Poll (Witte Software)

The reference implementation most engineers mean when they say "Modbus Poll." It opens multiple windows — one per slave connection — and lays out register data in a spreadsheet grid. You type a slave ID, a function code, a start address, and a quantity, and the grid populates and refreshes on a poll interval. Write a cell and it sends a Write Single Register (FC06) or Write Multiple Registers (FC16).

Its weakness is the same as every other tool in this list: it is Windows software. On macOS you run it through Parallels or a Windows VM, which is a heavy lift for a register-read utility. For the mechanics of reading registers, see our holding-register walkthrough.

Modscan / Modscan32

Modscan is the free grandparent of this category. For a single quick read of a few registers over serial it still works. But the interface is cramped, multi-window TCP sessions are awkward, and there has been no meaningful update in years. Use it if it is already installed on a Windows machine and you need a read in the next 30 seconds. Do not standardize a workflow on it.

Modbus Slave (the simulator half)

"Modbus Slave" means two things and people conflate them. The first is Witte Software's companion app to Modbus Poll — a slave simulator from the same vendor. The second is the general concept of a slave/server simulator. You need a simulator when the real device is not on your bench: you stand up a virtual power meter, point your master at it, and confirm your register map and scaling before you ever touch the field hardware.

The macOS Gap

All three legacy options assume Windows. If your laptop is a Mac — increasingly common for engineers who also design, document, and present — your choices historically were Parallels, a Remote Desktop into a Windows box, or a Java tool that sort-of worked. None of those is good.

MacTools Modbus Poll closes that gap. It is a native macOS app that does TCP and RTU, runs as a master and a slave simulator, and ships with real device templates — a Schneider PM5560 power meter, an SMA solar inverter, an ABB analyzer — so you can test against a realistic register map instead of a flat block of zeros. See the simulator comparison for the full device list.

Frequently Asked Questions

Is Modscan the same as Modbus Poll?

No. Modscan and Modbus Poll are separate Modbus master utilities from different authors. Modbus Poll is a Windows-only commercial tool from Witte Software. Modscan is an older Windows utility. Both act as a Modbus master to read and write registers, but Modbus Poll has a more active release cadence and broader feature set. Neither runs natively on macOS or Linux.

What is the difference between a Modbus master and a Modbus slave simulator?

A Modbus master (often called a poll tool) initiates requests — it reads and writes registers on slave devices. A Modbus slave simulator (slave server) responds to master requests and is used to emulate a device that does not exist physically. Many tools, including Modbus Poll and MacTools Modbus Poll, can run in both master and slave/simulator modes.

Is there a Modbus Poll alternative for macOS?

Yes. Modbus Poll by Witte Software is Windows-only. MacTools Modbus Poll is a native macOS app that reads and writes Modbus TCP and RTU registers, includes a slave simulator with real device templates (PM5560, SMA inverter, ABB analyzer), and costs $29.99 one-time. No Parallels or Windows VM required.

Is Modbus Poll free?

Modbus Poll by Witte Software has a free evaluation with a time-limited session and a nag screen; a single-user license is around $40. Modscan32 is free but unmaintained. MacTools Modbus Poll is $29.99 one-time with no subscription.

Further Reading

• Best Modbus Simulator in 2026: Free and Paid Tools Compared
• How to Read Modbus Holding Registers (FC03): A Practical Walkthrough
• How to Write Modbus Registers: FC06, FC16, and Coils
• Modbus Function Codes Explained: FC01–FC06, FC15, FC16