modbus-webui (beta)

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 install required to use the app; optional CLI for quick start.
Built with Svelte and shadcn.

Quick start

Directly from Github Pages

--> modbus-webUI <--

or with npx

# 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=...]

You can also download the single modbus-webui.html file and open it directly in a supported browser.

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 to allow future migrations.

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