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A web-based interface for CNC milling controller running Grbl, Marlin, Smoothieware, or TinyG.
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CNCjs Backers on Open Collective Sponsors on Open Collective Travis CI Build Status AppVeyor Build status Coverage Status

NPM cncjs

CNCjs is a full-featured web-based interface for CNC controllers running Grbl, Marlin, Smoothieware, or TinyG.

For a more complete introduction, see the Introduction section of the wiki page.



Custom Widgets


Boilerplate Code

Existing Pendants

Tablet UI

Browser Support

Yes Yes Yes Not supported Yes Yes

Supported Node.js Versions

Version Supported Level
4 Dropped support
6 Recommended for production use
8 Recommended for production use
9 Supported
10 Supported

Getting Started

Node.js Installation

Node.js 6 or higher is recommended. You can install Node Version Manager to manage multiple Node.js versions. If you have git installed, just clone the nvm repo, and check out the latest version:

git clone ~/.nvm
cd ~/.nvm
git checkout `git describe --abbrev=0 --tags`
cd ..
. ~/.nvm/

Add these lines to your ~/.bash_profile, ~/.bashrc, or ~/.profile file to have it automatically sourced upon login:

export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/" ] && . "$NVM_DIR/" # This loads nvm

Once installed, you can select Node.js versions with:

nvm install 6
nvm use 6

It's also recommended that you upgrade npm to the latest version. To upgrade, run:

npm install npm@latest -g


Install cncjs as a non-root user, or the serialport module may not install correctly on some platforms like Raspberry Pi.

npm install -g cncjs

If you're going to use sudo or root to install cncjs, you need to specify the --unsafe-perm option to run npm as the root account.

sudo npm install --unsafe-perm -g cncjs

Check out for other installation methods.


Run npm install -g cncjs@latest to install the latest version. To determine the version, use cncjs -V.


Run cncjs to start the server, and visit http://yourhostname:8000/ to view the web interface. Pass --help to cncjs for more options.

pi@rpi3$ cncjs -h

  Usage: cncjs [options]


    -V, --version                       output the version number
    -p, --port <port>                   Set listen port (default: 8000)
    -H, --host <host>                   Set listen address or hostname (default:
    -b, --backlog <backlog>             Set listen backlog (default: 511)
    -c, --config <filename>             Set config file (default: ~/.cncrc)
    -v, --verbose                       Increase the verbosity level (-v, -vv, -vvv)
    -m, --mount <route-path>:<target>   Add a mount point for serving static files
    -w, --watch-directory <path>        Watch a directory for changes
    --access-token-lifetime <lifetime>  Access token lifetime in seconds or a time span string (default: 30d)
    --allow-remote-access               Allow remote access to the server (default: false)
    --controller <type>                 Specify CNC controller: Grbl|Marlin|Smoothie|TinyG|g2core (default: '')
    -h, --help                          output usage information


    $ cncjs -vv
    $ cncjs --mount /pendant:/home/pi/tinyweb
    $ cncjs --mount /widget:~+/widget --mount /pendant:~/pendant
    $ cncjs --mount /widget:
    $ cncjs --watch-directory /home/pi/watch
    $ cncjs --access-token-lifetime 60d  # e.g. 3600, 30m, 12h, 30d
    $ cncjs --allow-remote-access
    $ cncjs --controller Grbl

Instead of passing command line options for --watch-directory, --access-token-lifetime, --allow-remote-access, and --controller, you can create a ~/.cncrc file that contains the following configuration in JSON format:

    "mountPoints": [
            "route": "/pendant",
            "target": "/home/pi/tinyweb"
            "route": "/widget",
            "target": ""
    "watchDirectory": "/path/to/dir",
    "accessTokenLifetime": "30d",
    "allowRemoteAccess": false,
    "controller": ""

To troubleshoot issues, run:

cncjs -vvv

Configuration File

The configuration file .cncrc contains settings that are equivalent to the cncjs command-line options. The configuration file is stored in user's home directory. To find out the actual location of the home directory, do the following:

  • Linux/Mac

    echo $HOME
  • Windows

    echo %USERPROFILE%

Check out an example configuration file here.

File Format

See for a detailed explanation.

  "ports": [
       "comName": "/dev/ttyAMA0",
       "manufacturer": ""
  "baudrates": [115200, 250000],
  "mountPoints": [
      "route": "/widget",
      "target": ""
  "watchDirectory": "/path/to/dir",
  "accessTokenLifetime": "30d",
  "allowRemoteAccess": false,
  "controller": "",
  "state": {
    "checkForUpdates": true,
    "controller": {
      "exception": {
        "ignoreErrors": false
  "commands": [
      "title": "Update (root user)",
      "commands": "sudo npm install -g cncjs@latest --unsafe-perm; pkill -a -f cncjs"
      "title": "Update (non-root user)",
      "commands": "npm install -g cncjs@latest; pkill -a -f cncjs"
      "title": "Reboot",
      "commands": "sudo /sbin/reboot"
      "title": "Shutdown",
      "commands": "sudo /sbin/shutdown"
  "events": [],
  "macros": [],
  "users": []



There are several *.gcode files in the examples directory. You can use the GCode widget to load a GCode file and make a trial run.

If you don't have a CAM software, try using jscut to create G-Code from *.svg. It's a simple CAM package that runs in the browser.

Check out a live demo at


Use GitHub issues for requests.

Pull requests welcome! Learn how to contribute.


You can help translate resource files in both of app and web directories from English to other languages. Check out Localization guide to learn how to get started. If you are not familiar with GitHub development, you can open an issue or send your translations to

Locale Language Status Contributors
cs Čeština (Czech) Miroslav Zuzelka
de Deutsch (German) Thorsten Godau, Max B.
es Español (Spanish) Juan Biondi
fr Français (French) Simon Maillard, CorentinBrulé
hu Magyar (Hungarian) Sipos Péter
it Italiano (Italian) vince87
ja 日本語 (Japanese) Naoki Okamoto
nl Nederlands (Netherlands) dutchpatriot
pt-br Português (Brasil) cmsteinBR
ru Ру́сский (Russian) Denis Yusupov
tr Türkçe (Turkish) Ali GÜNDOĞDU
zh-cn 简体中文 (Simplified Chinese) Mandy Chien, Terry Lee
zh-tw 繁體中文 (Traditional Chinese) Cheton Wu


If you would like to support this project, you can make a donation using PayPal. Thank you!



This project exists thanks to all the people who contribute. [Contribute].


Thank you to all our backers! 🙏 [Become a backer]


Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [Become a sponsor]


Licensed under the MIT License.

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