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Dead Simple LESS CSS Watch Compiler

A command that watches folders(and subfolders) for file changes and automatically compile the less css files into css. This is a file system watcher and compiler. It also keep track of a dependency tree and recompiles the parent if an imported (child) LESS file is changed.

Parts of this script is modified from Mikeal Rogers's watch script (


Install LESS and make sure the lessc binary is accessible to the script. Installing LESS with the -g(global) flag will make the binary accessible to your system.

Use yarn

(sudo) yarn global add less

or npm

(sudo) npm install -g less


Install the less-watch-compiler command globally.

Use yarn

(sudo) yarn global add

or npm

(sudo) npm install -g less-watch-compiler


With no main file

You need to pass in the minimum 2 parameters - <source_dir> and <destination_dir> . First parameter is the source folder to watch for changes and second is the output folder in which the css files will be compiled


less-watch-compiler [options] <source_dir> <destination_dir> [main_file_name]

With main file

If you pass in the 3rd optional parameter, Any file change will trigger only to compile the main file specified in the 3rd parameter. Assuming the 3rd is "main.less"


	input folder: src
	|____ src
	|________ main.less (import aux.less)
	|________ aux.less
	 output folder: dist
	|____ dist
	|________ main.css

Real usage:

less-watch-compiler src dist main.less

Example #1

less-watch-compiler tests/less tests/css

The above command will watch the tests/less folder and compile the LESS CSS files into tests/css folder as soon as they are added/updated.

Example #2

Add less-watch-compiler.config.json as follows in your project folder

    "minified": false,
    "sourceMap": false,
    "plugins": "less_plugin1,less_plugin2",
    "watchFolder": "tests/less",
    "outputFolder": "tests/css"

The above will do the same as in example 1. But you can just run the following without passing the folders everytime.



-h, --help                       output usage information
-V, --version                    output the version number
--source-map                     Generate source map for css files
--main-file <file>               Specify <file> as the file to always re-compile e.g. '--main-file style.less'
--plugins <plugin-a>,<plugin-b>  List of plugins separated by commas


  • By default, "minified" is turned on to always compress/minify output. You can set the minification to false by adding "minified":false in the config file.
  • By default, "sourceMap" is turned off. You can generating sourcemap to true by adding "sourceMap":true in the config file.
  • By default, this script only compiles files with .less extension. More file extensions can be added by modifying the allowedExtensions array in config.json.
  • Files that start with underscores _style.css or period .style.css are ignored. This behavior can be changed in the filterFiles() function.

Using the source files

Alternativelly, you can checkout the code and run things locally like this:

node less-watch-compiler.js [options]

To run unit tests: yarn test or npm test (see tests/test.js).