ModbusLens

Everything you need to
talk to a Modbus device

Free Modbus TCP and RTU client for engineers working with industrial automation systems. Communication, live tag monitoring, trend graphing, a device simulator, and network diagnostics - in one tool.

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ModbusLens register scanner showing a color-coded results grid

What it does

MULTI-DEVICE

Every device at a glance

  • Overview tab: one card per device - live status, success rate, latency and pinned values
  • Each device has its own connection and Unit ID; devices behind one gateway share one link
  • Select devices in the top bar for Device Settings and Connect/Disconnect Selected, or check a card to Remove Selected
  • Tags, Trend pens and Raw Data are per device, with device tabs and filters
  • Address Table, Script, Scanner and diagnostics each pick their own device

COMMUNICATION

Modbus TCP & RTU

  • TCP or Serial (RTU/ASCII) client, multiple simultaneous connections
  • Auto-reconnect with backoff, monitoring resumes on its own
  • Fast LAN Mode for quick failure detection over TCP
  • RTU-over-TCP framing for transparent serial-to-Ethernet gateways
  • Save/Load a full session, or just Tags via CSV

DATA HANDLING

Decode it your way

  • BOOL, U16/S16, U32/S32/F32, U64/S64/F64, HEX
  • Word-order swap handling for 32- and 64-bit formats
  • 0-based or 1-based addressing, per range or per tag
  • Raw hex shown alongside every decoded value

MONITORING

Live tag monitoring

  • Read/Write/Timestamp, alarms, and engineering-unit scaling in one table
  • Drag-and-drop reorder, multi-select Write Selected / Write All
  • Per-tag Enabled toggle, column show/hide and reorder
  • Per-tag alarms with red highlighting
  • Bit View - name and read/write individual bits within a register
  • Log live values to CSV

PROFILES

Device Profiles

  • Save a device's Address Table range and Tags as one named, reusable template
  • View Profile shows which tags are already in your live list before you import any
  • Browse and download profiles shared by other users, or share your own back - no account needed

DIAGNOSTICS

Raw Data

  • Every transaction logged - time, value, hex, success/failure, latency
  • The actual TX/RX bytes off the wire, not just decoded values
  • Live filtering plus a full statistics breakdown
  • Frame Viewer decodes each TX/RX frame field by field, with plain-English Modbus exception explanations

TRENDING

Trend graphing

  • Up to 20 pens, picked straight from your Tags list, with pages and per-device pens
  • Detachable window, zoom/pan, live crosshair and stats
  • Record a session and replay it later at 1x-8x speed

SIMULATION

Server mode

  • Act as a Modbus TCP slave for testing your own SCADA/PLC program
  • Coils, discrete inputs, holding & input registers all editable live
  • Gateway mode - relay real requests to a real serial device over TCP

AUTOMATION

Scripting

  • Purpose-built test-sequence language - no imports, no exceptions to write
  • WRITE, READ, WAIT, LOG, LET, REPEAT, IF, ASSERT, a live Variables panel, and a DEVICE command to switch mid-run
  • Target a real connected device or the built-in Server simulator

NETWORK

Network diagnostics

  • Fast parallel TCP discovery scan, sized to your real subnet
  • Optional ARP mode (MAC/vendor lookup) and packet capture via Npcap
  • Optional Unit ID sweep (1-247) per discovered host to report which IDs respond
  • Unified Find Devices panel: TCP scan and serial parameter sweep share one results table

SERIAL

Serial discovery

  • Sweeps baud/parity/stop-bit combinations and Unit ID range to find an undocumented device's settings
  • Jump straight in from Connection Settings' Serial section with the COM port already filled in

COMPLIANCE

Diagnostic functions

  • FC07, 08, 11/12, 17, 20/21, 22, 24, and 43 in one function picker
  • For compliance and interop testing beyond basic read/write

DECODER

Data decoder

  • Paste raw hex, see U16 to F64, HEX, binary, ASCII, BCD and individual bits at once
  • All four byte/word orders (ABCD/BADC/CDAB/DCBA), no connection needed

SCANNING

Register scanner

  • Auto-discovers which addresses respond for Coils, Discrete, Holding, or Input Registers
  • Results shown as a color-coded grid with a legend (green = responds, red = no response, amber = timed out - inconclusive), paginated like spreadsheet sheets for large ranges
  • Adjustable text size and a colorblind-friendly color option
  • A timeout on one address narrows down and keeps scanning instead of stopping the whole range
  • Create Tags From Scan - turn responding addresses into Tags-tab rows in one click

INTERFACE

Built for the job

  • Light / Dark / Follow System theme - switching never force-disconnects a live device, it queues and asks to restart once everything's disconnected
  • Color-coded logs, and Ctrl+scroll zoom on logs and tables
  • Built-in update checker against GitHub Releases

How it compares

Most classic Modbus tools split the job across separate master/slave apps with no discovery, scripting, or trending built in. ModbusLens keeps it one tool. Feature availability shown for other tools reflects their publicly documented capabilities as of this writing - always verify against their current release before relying on it.

Feature ModbusLens Modbus Poll + Slave ModScan Simply Modbus QModMaster
Modbus Client (Master)✔✔✔✔✔
Modbus Server (Slave), same app✔ built-in⚠ separate app⚠ separate app⚠ separate app✖
Raw Data / Frame Viewer (wire bytes, exception decode)✔⚠ basic log✖✖✖
Trend Graphing & Record/Replay✔ advanced⚠ basic✖✖✖
Built-in Test Scripting (WRITE/READ/WAIT/IF/REPEAT/ASSERT)✔✖✖✖✖
Network + Serial Device Discovery✔✖✖✖✖
Full Session Save/Load (connection, tags, ranges, write bounds)✔⚠ partial✖⚠ partial✖
Device Profiles (save, reuse, and share templates with the Community)✔✖✖✖✖
Free & Open Source✔✖ paid✖ paid✖ paid✔
Unified Single Application✔✖✖✖⚠ master only

✔ full support · ⚠ partial/limited · ✖ not available

Screenshots

Raw Data view
Raw Data view
Tags monitoring
Trend graphing
Script tab running a test sequence
Register scanner showing a color-coded results grid
Overview tab with two meters online, live values and per-device status

Download ModbusLens

Get the latest version   for your platform

Get ModbusLens

Download Installer Download Portable EXE

Installer recommended - the portable exe can fail to start on some machines (non-ASCII Windows usernames, or antivirus interfering with how it unpacks itself).

System Requirements

  • Windows 10 or newer, 64-bit
  • Admin rights for the installer (one UAC prompt during setup)
  • Npcap - optional, only needed for ARP-based discovery and packet capture