3.0.0 • Public • Published

grunt-contrib-less v3.0.0 Build Status

Compile LESS files to CSS

Getting Started

If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a Gruntfile as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:

npm install grunt-contrib-less --save-dev

Once the plugin has been installed, it may be enabled inside your Gruntfile with this line of JavaScript:


This plugin was designed to work with Grunt 0.4.x. If you're still using grunt v0.3.x it's strongly recommended that you upgrade, but in case you can't please use v0.3.2.

Less task

Run this task with the grunt less command.

Task targets, files and options may be specified according to the grunt Configuring tasks guide.



Type: String Array Function
Default: Directory of input file.

Specifies directories to scan for @import directives when parsing. Default value is the directory of the source, which is probably what you want.

If you specify a function the source filepath will be the first argument. You can return either a string or an array of paths to be used.


Type: String
Default: ""

A path to add on to the start of every URL resource.


Type: Boolean
Default: false

Compress output by removing some whitespaces.


Type: Array
Default: null

Allows passing plugins.


Type: Integer
Default: null

Set the parser's optimization level. The lower the number, the less nodes it will create in the tree. This could matter for debugging, or if you want to access the individual nodes in the tree.


Type: Boolean
Default: false

Force evaluation of imports.


Type: Boolean
Default: false

When enabled, math is required to be in parenthesis.


Type: Boolean
Default: false

When enabled, less will validate the units used (e.g. 4px/2px = 2, not 2px and 4em/2px throws an error).


Type: Boolean
Default: false

Read @import'ed files synchronously from disk.


Type: String
Default: false

Configures -sass-debug-info support.

Accepts following values: comments, mediaquery, all.


Type: Boolean
Default: false

Rewrite URLs to be relative. false: do not modify URLs.


Type: Object
Default: none

Define custom functions to be available within your LESS stylesheets. The function's name must be lowercase. In the definition, the first argument is the less object, and subsequent arguments are from the less function call. Values passed to the function are types defined within less, the return value may be either one of them or primitive. See the LESS documentation for more information on the available types.


Type: Boolean
Default: false

Enable source maps.


Type: String
Default: none

Write the source map to a separate file with the given filename.


Type: String
Default: none

Override the default URL that points to the source map from the compiled CSS file.


Type: String
Default: none

Sets the base path for the less file paths in the source map.


Type: String
Default: none

Adds this path onto the less file paths in the source map.


Type: Boolean
Default: false

Puts the map (and any less files) as a base64 data uri into the output css file.


Type: Boolean
Default: false

Puts the less files into the map instead of referencing them.


Type: Object
Default: none

Overrides global variables. Equivalent to --modify-vars='VAR=VALUE' option in less.


Type: String
Default: none


Type: Function(content, destinationPath) Default: none Attributes: content, destinationPath

Allows to parse the CSS content to be written to destinationPath to flow through a self defined function.

Usage Examples

less: {
  development: {
    options: {
      paths: ['assets/css']
    files: {
      'path/to/result.css': 'path/to/source.less'
  production: {
    options: {
      paths: ['assets/css'],
      plugins: [
        new (require('less-plugin-autoprefix'))({browsers: ["last 2 versions"]}),
        new (require('less-plugin-clean-css'))(cleanCssOptions)
      modifyVars: {
        imgPath: '""',
        bgColor: 'red'
    files: {
      'path/to/result.css': 'path/to/source.less'

Release History

  • 2021-02-21   v3.0.0   Updated to Less 4. ieCompat option removed.
  • 2021-02-20   v2.1.0   Dependency updates. New process option to modify the written CSS.
  • 2018-05-25   v2.0.0   Update less to ^3.0.0
  • 2017-03-08   v1.4.1   Fix sourceMappingURL to be the same as the CSS if not specified, #322. Rethrow the compilation error after printing the message, #315.
  • 2016-07-21   v1.4.0   Update async and less to ~2.7.1.
  • 2016-04-07   v1.3.0   Update lodash and async dependecies.
  • 2016-02-01   v1.2.0   Update to less ~2.6.0. Removed peerDependency from package.json.
  • 2015-11-09   v1.1.0   Update to less ~2.5.0.
  • 2014-12-23   v1.0.0   Update to less 2.1.0.
  • 2014-10-23   v0.12.0   Added cleancssOptions as an option. When possible, includes filename for failed writes. Ensure banner only outputs on the first file in a series.
  • 2014-07-29   v0.11.4   Fix banner and urlArgs LESS options. Fixes npm 2 peerDependencies issues.
  • 2014-06-20   v0.11.3   Update to Less ~1.7.2.
  • 2014-06-01   v0.11.2   Lock to less 1.7.0.
  • 2014-05-26   v0.11.1   Fix modifyVars to work when less file ends with a comment.
  • 2014-03-19   v0.11.0   Custom functions can return types defined by less. paths option now accepts a function. Replaced deprecated grunt.util methods. Removes deprecated grunt.lib.contrib.
  • 2014-03-01   v0.10.0   sourceMapBasepath accepts a function. Update copyright to 2014. Update .gitattributes. Update less.js to v1.7.0. Prevent CRLF in the repo. Adds modify-vars option. Changed to async stack call. Fixes data-uri test. Normalize line endings on tests.
  • 2014-01-07   v0.9.0   Bump to less 1.6.
  • 2013-12-06   v0.8.3   Support sourceMapURL.
  • 2013-11-14   v0.8.2   Support outputSourceFiles.
  • 2013-10-24   v0.8.1   Support sourceMapFilename, sourceMapBasepath and sourceMapRootpath.
  • 2013-10-22   v0.8.0   Upgrade to LESS 1.5. Support strictUnits option. Support sourceMap option. Add customFunctions option for defining custom functions within LESS. Output the source file name on error. yuicompress option now cleancss (Less changed underlying dependency)
  • 2013-08-08   v0.7.0   Downgrade no source files warning to only in verbose mode.
  • 2013-08-08   v0.6.5   Support strictMath option. Support rootpath parse option.
  • 2013-07-09   v0.6.4   Support relativeUrls option.
  • 2013-07-06   v0.6.3   Add report option for minification and gzip results.
  • 2013-07-03   v0.6.2   support syncImport.
  • 2013-06-12   v0.6.1   Support ieCompat.
  • 2013-06-09   v0.6.0   Bump less to 1.4.0.
  • 2013-05-23   v0.5.2   Improve error handling.
  • 2013-04-25   v0.5.1   Gracefully handle configuration without sources.
  • 2013-02-15   v0.5.0   First official release for Grunt 0.4.0.
  • 2013-01-23   v0.5.0rc7   Updating grunt/gruntplugin dependencies to rc7. Changing in-development grunt/gruntplugin dependency versions from tilde version ranges to specific versions. Remove experimental wildcard destination support. Switching to this.files API.
  • 2012-10-18   v0.3.2   Add support for dumpLineNumbers.
  • 2012-10-12   v0.3.1   Rename grunt-contrib-lib dep to grunt-lib-contrib.
  • 2012-09-24   v0.3.0   Global options depreciated. Revert normalize linefeeds.
  • 2012-09-16   v0.2.2   Support all less options. Normalize linefeeds. Default path to dirname of src file.
  • 2012-09-10   v0.2.0   Refactored from grunt-contrib into individual repo.

Task submitted by Tyler Kellen

This file was generated on Sun Feb 21 2021 11:29:25.



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