modbus-webui

Single-file Modbus workbench — profiles, name tables, shortcuts.

What it is

A browser-based UI for Modbus devices. Runs fully client-side via the Web Serial API and modbus-webserial. No backend required.

Quick start

Use hosted app (GitHub Pages)

modbuswebui.dev

Offline/local use (no npm or npx)

1. Download the latest modbus-webui.html from the GitHub releases.
2. Open modbus-webui.html directly in a supported Chromium-based desktop browser.
3. Optional: host the same file on your internal/static server.

Optional CLI convenience

# serve the packaged HTML immediately
npx modbus-webui start

# or write the HTML to your cwd, then serve it
npx modbus-webui init
npx modbus-webui serve
# options:
#   --port=5173
#   init [filename] [--force]
#   serve [filename] [--port=...]

Security & privacy

• No Google Analytics or tracking scripts are injected into the app.
• No backend dependency: Modbus communication is from your browser to your selected serial port.
• Offline-capable: the same single HTML file can be used in fully isolated local environments.
• One-click download: use the in-app footer link to download modbus-webui.html for local reuse.
• Self-hosting friendly: you can host a vetted static artifact in your own network.

Features

• Read / write coils and registers
• Profiles: per-device settings + saved write shortcuts
• Name tables: global sets covering coils, discrete inputs, holding and input registers
• Shortcuts: one-click saved writes
• Local persistence: everything stored in your browser

Basic usage

1. Click Connect and choose your serial port.
2. Set port parameters (baud, parity, etc.) and click Open.
3. Use Read / Write panels to operate coils and registers.
4. Save frequent actions as Shortcuts and run them from the Shortcuts panel.
5. Use Name Tables to label addresses; Profiles keep device-specific setup.

Concepts

Profiles

• Hold your selected name-table set, connection settings, and write shortcuts.
• Changes apply immediately to the active profile. Switching profiles does not disconnect the port.

Name tables

• Stored globally; any profile can select a set to use.
• Cover all four areas: coils, discrete inputs, holding registers, input registers.
• Names are linked to addresses (enter as decimal or hex). Edit via the Name Tables modal or copy/paste a full set as JSON.

Storage & versioning

• All data is kept as a single library and saved to localStorage (auto or manual save).
• The stored data is versioned with a strong migration layer, so old library storage files are intended to stay migration-proof across app updates.

Browser support

• Requires Chromium-based desktop browsers with Web Serial enabled.
• You grant port access per session; after reload you may need to select the port again.
• The app will show a notice if Web Serial isn’t available.

Development

# install
npm i

# dev
npm run dev

# build (emits dist/modbus-webui.html)
npm run build