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Enable LESS CSS in WordPress

LESS is an abstraction layer that adds some very powerful features to CSS. It will speed up your development process and make your life that much easier. Find out more from the links below and then head on back.

The addon allows you to write and edit .less files directly and have WordPress do the job of compiling and caching the resulting CSS. It eliminates the extra step of having to compile the .less files into CSS yourself before deploying them.


If you are using git to clone the repository, do the following:

git clone git:// wp-less

If you are downloading the .zip or .tar, don't forget to download the lessphp dependency too and copy it into the vendor/leafo/lessphp directory.

Then install the lessphp dependency using:

composer install

Alternatively, add "icit/wp-less" as a requirement to your composer.json, and add this git repository e.g.:

    "repositories": [
            "type": "git",
            "url": ""
    "require": {
        "icit/wp-less": "dev-master"


You can either install the script as a standard plugin or use it as an include within a theme or plugin.

For use with themes add the following lines to your functions.php:


// Include the class (unless you are using the script as a plugin)
require_once( 'wp-less/wp-less.php' );

// enqueue a .less style sheet
if ( ! is_admin() )
    wp_enqueue_style( 'style', get_stylesheet_directory_uri() . '/style.less' );

// you can also use .less files as mce editor style sheets
add_editor_style( 'editor-style.less' );

Any registered styles with the .less suffix will be compiled and the file URL rewritten.

You won't need a link to your main style sheet in header.php. Just make sure that wp_head() is called in the document head.

All the standard LESS features are supported as well as @import rules anywhere within the file.

Passing in variables from PHP

You can pass variables into your .less files using the less_vars hook or with the functions defined in the PHP Interface section:


// pass variables into all .less files
add_filter( 'less_vars', 'my_less_vars', 10, 2 );
function my_less_vars( $vars, $handle ) {
    // $handle is a reference to the handle used with wp_enqueue_style()
    $vars[ 'color' ] = '#000000';
    return $vars;


Within your .less files you can use the variable as if you had declared it in the stylesheet. For e.g.:

body { color: @color; }

Default variables

There are 2 default variables you can use without worrying about the above code:

@themeurl is the URL of the current theme directory:

body { background-image: url(@{themeurl}/images/background.png); }

@lessurl* is the URL of the enqueued LESS file (this does not change inside imported files):

.plugin-title { background-image: url(@{lessurl}/images/icon.png); }

@lessurl is useful in those cases where you have .less files inside plugins or other non theme folder locations.

It is important to use these because you can't use relative paths - the compiled CSS is stored in the uploads folder as it is the only place you can guarantee being able to write to in any given WordPress installation. As a result relative URLs will break.

PHP interface

register_less_function() allows you to create additional less compiler functions for use in your stylesheet without having to touch the lessc class yourself.

register_less_function( 'double', function( $args ) {
    list( $type, $value, $unit ) = $args;
	return array( $type, $value*2, $unit );
} );

unregister_less_function() works in a similar way but unregisters any compiler functions passed to it by name.

unregister_less_function( 'double' );

add_less_var() makes it easy to create or modify variables passed into the compiler. Both arguments should be a string, as lessc will work out the type of variable it is.

add_less_var( 'brandcolour', '#ec6704' );

remove_less_var() is the inverse of add_less_var() and only requires the variable name to remove.

remove_less_var( 'brandcolour' );

Further Reading

Read the LESS.js documentation here.

Read the documentation specific to the PHP parser here.


Big massive thanks to those whose contributions and discussion has helped to improve the plugin.


The software is licensed under the MIT Licence.


Provides a LESS compiler compatible with wp_enqueue_style() for rapid CSS development in themes and plugins.




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