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    2.5.1 • Public • Published

    Bootstrap Less

    Bootstrap version npm version

    This is a Less port of Bootstrap v4, since Bootstrap now uses Sass for CSS preprocessing. This is purely a Sass→Less port: it doesn’t modify or build on the default Bootstrap styles in any way.

    The code is currently aligned with Bootstrap v4.6.0. It requires Less v3.9.0 or above to compile. Note: For Less versions below v3.9.0, you can use v1.0.0 of the port, which is compatible with Less >=2.6.0.

    Getting Started

    Options for installing Bootstrap Less in your project (note that Less v3.9.0 or above is required):

    • Install with npm: npm install bootstrap-less-port
    • Install with yarn: yarn add bootstrap-less-port
    • Install with bower (not recommended): bower install bootstrap-less-port
    • Clone the repo: git clone
    • Download the latest release

    Note that this code is only necessary if you want to use Less in your project and want to import and/or customize Bootstrap’s variables, mixins or styles. If you plan to use the CSS framework wholesale, you can get the compiled CSS files from the main Bootstrap repo, so there’s no need for this code.


    To use these files in your project, simply import them into your main Less file. For example, if you’ve installed Bootstrap Less using npm or Yarn, you might have a file structure that looks like this:

     ├─ less/
     │   └─ custom.less
     └─ node_modules/
         └─ bootstrap-less-port/
             └─ less/
                 └─ ...

    In this case, you could then import what you need into custom.less using module-relative paths:

    // custom.less
    // Required Files
    @import "bootstrap-less-port/less/_functions";
    @import "bootstrap-less-port/less/_variables";
    @import "bootstrap-less-port/less/_mixins";
    // Optional Files
    @import "bootstrap-less-port/less/_reboot";
    @import "bootstrap-less-port/less/_utilities";
    @import "bootstrap-less-port/less/_type";
    @import "bootstrap-less-port/less/_grid";

    This approach is recommended since it will result in a smaller CSS file by omitting the styles you don’t need. (Just be aware that some files are dependent on others.)

    Alternatively, you can get the entire framework by simply importing the package as a whole. (Or, if not using a package manager, importing bootstrap-less-port/less/bootstrap instead.)

    // custom.less
    @import "bootstrap-less-port";


    The recommended way of customizing Bootstrap is to override the default variables. To override a variable, copy and paste it from _variables.less into your custom Less file and change its value.

    // custom.less
    @import "bootstrap-less-port";
    // Variable Overrides
    @body-bg: @black;
    @body-color: @white;

    Variable overrides can be included in any file as long as they are imported after the Bootstrap Less files; Less will use the last value assigned to a variable.

    For a more in-depth guide to theming, see the Bootstrap docs.


    This repo does not include the JavaScript component files from Bootstrap v4. If you’d like to use them the easiest way to do so is via Bootstrap CDN. Otherwise, you can get the files from the main Bootstrap repo by downloading it or installing it using a package manager.


    See the Bootstrap v4 docs for documentation.


    This port attempts to mirror the source Sass files as closely as possible in order to make updating it straight-forward. This means that variable/mixin naming, custom functions and most code style match the original project with a few notable exceptions:

    1. Mixins Mixins work the same as they did in previous Bootstrap versions with the exception that they now use ID selectors instead of class selectors (e.g. .border-radius() is now #border-radius()). This was done to avoid potential collisions with the user’s class names.

      Variables within mixins are named the same as their Sass counterparts whenever possible, in order to make comparison with the Sass version easier.

    2. Custom functions Sass allows for custom functions to be written in the sass files themselves, which isn’t possible in Less. All custom functions have been replaced with Less plugins that add equivalent functions to the language. These plugins are located in less/plugins/ as JavaScript files.

      Plugins have also been added to duplicate some native Sass functions for simplicity.

      Note: The plugins are included using the @plugin at-rule instead of as arguments to the lessc CLI. This was intentionally done since most Less GUI compilers don’t allow you to customize the command-line arguments.

    3. Loops Where possible, Sass @each loops have been replaced with the Less each() function. Sass @for directives have been replaced by each() together with the range() function.

      In order to make catching bugs easier, the Sass versions of most for/each loops have been kept in the code, commented, above the Less versions.

    4. Placeholder selectors Since Less has no equivalent for Sass’ placeholder selectors, regular selectors are used instead. In order to prevent name clashes with selectors in users’ code, element selectors prefixed with an escaped % are used instead (for example \%grid-column).

    5. Code style While the code style is mostly identical to that used by Bootstrap, a few changes have been made:

      • Tabs are used instead of spaces
      • Leading zeros have been added to decimal numbers for readability
      • Spaces have been added between the values of comma-separated lists, also for readability


    For bugs, feature-requests, or issues with the compiled CSS, please create an issue in the main Bootstrap repo.

    For errors or bugs related to the ported code, please submit a pull request or create an issue.

    Credits and License

    Bootstrap was created by Mark Otto and Jacob Thornton.

    The original code copyright 2011-2019 the Bootstrap Authors and Twitter, Inc.

    This port and the original code are released under the MIT License.


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