Using LESS with Bootstrap
Customize and extend Bootstrap with LESS, a CSS preprocessor, to take advantage of the variables, mixins, and more used to build Bootstrap's CSS.
Built with LESS
Why LESS?
Bootstrap is made with LESS at it's core, a dynamic stylesheet language created by our good friend, Alexis Sellier. It makes developing systems-based CSS faster, easier, and more fun.
What's included?
As an extension of CSS, LESS includes variables, mixins for reusable snippets of code, operations for simple math, nesting, and even color functions.
Variables
Managing colors and pixel values in CSS can be a bit of a pain, usually full of copy and paste. Not with LESS though—assign colors or pixel values as variables and change them once.
Mixins
Those three border-radius declarations you need to make in regular ol' CSS? Now they're down to one line with the help of mixins, snippets of code you can reuse anywhere.
Operations
Make your grid, leading, and more super flexible by doing the math on the fly with operations. Multiple, divide, add, and subtract your way to CSS sanity.
Bootstrap variables
Hyperlinks
| Variable | Value | Usage |
|---|---|---|
@linkColor |
#08c | Default link text color |
@linkColorHover |
darken(@linkColor, 15%) |
Default link text hover color |
Grayscale colors
| Variable | Value |
|---|---|
@black |
#000 |
@grayDarker |
#222 |
@grayDark |
#333 |
@gray |
#555 |
@grayLight |
#999 |
@grayLighter |
#eee |
@white |
#fff |
Accent colors
| Variable | Value |
|---|---|
@blue |
#049cdb |
@green |
#46a546 |
@red |
#9d261d |
@yellow |
#ffc40d |
@orange |
#f89406 |
@pink |
#c3325f |
@purple |
#7a43b6 |
Grid system
| Variable | Value |
|---|---|
@gridColumns |
12 |
@gridColumnWidth |
60px |
@gridGutterWidth |
20px |
@siteWidth |
(@gridColumns * @gridColumnWidth) + (@gridGutterWidth * (@gridColumns - 1)) |
Typography
| Variable | Value | |
|---|---|---|
@baseFontSize |
13px | |
@baseFontFamily |
"Helvetica Neue", Helvetica, Arial, sans-serif |
|
@baseLineHeight |
18px |
Components
Buttons
@primaryButtonBackground |
@linkColor |
Forms
@placeholderText |
@grayLight |
Navbar
@navbarHeight |
40px |
@navbarBackground |
@grayDarker |
@navbarBackgroundHighlight |
@grayDark |
Form states and alerts
@warningText |
#f3edd2 |
@warningBackground |
#c09853 |
@warningBorder |
#f3edd2 |
@errorText |
#b94a48 |
@errorBackground |
#f2dede |
@errorBorder |
#e9c7c7 |
@successText |
#468847 |
@successBackground |
#dff0d8 |
@successBorder |
#cfe8c4 |
@infoText |
#3a87ad |
@infoBackground |
#d9edf7 |
@infoBorder |
#bfe1f2 |
Bootstrap mixins
About mixins
Basic mixins
A basic mixin is essentially an include or a partial for a snippet of CSS. They're written just like a CSS class and can be called anywhere.
.element {
.clearfix();
}
Parametric mixins
A parametric mixin is just like a basic mixin, but it also accepts parameters (hence the name) with optional default values.
.element {
.border-radius(4px);
}
Easily add your own
Nearly all of Bootstrap's mixins are stored in mixins.less, a wonderful utility .less file that enables you to use a mixin in any of the .less files in the toolkit.
So, go ahead and use the existing ones or feel free to add your own as you need.
Included mixins
Utilities
| Mixin | Parameters | Usage |
|---|---|---|
.clearfix() |
none | Add to any parent to clear floats within |
.center-block() |
none | Auto center a block-level element using margin: auto |
.ie7-inline-block() |
none | Use in addition to regular display: inline-block to get IE7 support |
.size() |
@height: 5px, @width: 5px |
Quickly set the height and width on one line |
.square() |
@size: 5px |
Builds on .size() to set the width and height as same value |
.opacity() |
@opacity: 100 |
Set, in whole numbers, the opacity percentage (e.g., "50" or "75") |
Forms
| Mixin | Parameters | Usage |
|---|---|---|
.placeholder() |
@color: @placeholderText |
Set the placeholder text color for inputs |
Typography
| Mixin | Parameters | Usage |
|---|---|---|
#font > #family > .serif() |
none | Make an element use a serif font stack |
#font > #family > .sans-serif() |
none | Make an element use a sans-serif font stack |
#font > #family > .monospace() |
none | Make an element use a monospace font stack |
#font > .shorthand() |
@size: @baseFontSize, @weight: normal, @lineHeight: @baseLineHeight |
Easily set font size, weight, and leading |
#font > .serif() |
@size: @baseFontSize, @weight: normal, @lineHeight: @baseLineHeight |
Set font family to serif, and control size, weight, and leading |
#font > .sans-serif() |
@size: @baseFontSize, @weight: normal, @lineHeight: @baseLineHeight |
Set font family to sans-serif, and control size, weight, and leading |
#font > .monospace() |
@size: @baseFontSize, @weight: normal, @lineHeight: @baseLineHeight |
Set font family to monospace, and control size, weight, and leading |
Grid system
| Mixin | Parameters | Usage |
|---|---|---|
.container-fixed() |
none | Provide a fixed-width (set with @siteWidth) container for holding your content |
.columns() |
@columns: 1 |
Build a grid column that spans any number of columns (defaults to 1 column) |
.offset() |
@columns: 1 |
Offset a grid column with left margin that spans any number of columns |
.gridColumn() |
none | Make an element float like a grid column |
CSS3 properties
| Mixin | Parameters | Usage |
|---|---|---|
.border-radius() |
@radius: 5px |
Round the corners of an element. Can be a single value or four space-separated values |
.box-shadow() |
@shadow: 0 1px 3px rgba(0,0,0,.25) |
Add a drop shadow to an element |
.transition() |
@transition |
Add CSS3 transition effect (e.g., all .2s linear) |
.rotate() |
@degrees |
Rotate an element n degrees |
.scale() |
@ratio |
Scale an element to n times it's original size |
.translate() |
@x: 0, @y: 0 |
Move an element on the x and y planes |
.background-clip() |
@clip |
Crop the backgroud of an element (useful for border-radius) |
.background-size() |
@size |
Control the size of background images via CSS3 |
.box-sizing() |
@boxmodel |
Change the box model for an element (e.g., border-box for a full-width input) |
.user-select() |
@select |
Control cursor selection of text on a page |
.resizable() |
@direction: both |
Make any element resizable on the right and bottom |
.content-columns() |
@columnCount, @columnGap: @gridColumnGutter |
Make the content of any element use CSS3 columns |
Backgrounds and gradients
| Mixin | Parameters | Usage |
|---|---|---|
.#translucent > .background() |
@color: @white, @alpha: 1 |
Give an element a translucent background color |
.#translucent > .border() |
@color: @white, @alpha: 1 |
Give an element a translucent border color |
.#gradient > .vertical() |
@startColor, @endColor |
Create a cross-browser vertical background gradient |
.#gradient > .horizontal() |
@startColor, @endColor |
Create a cross-browser horizontal background gradient |
.#gradient > .directional() |
@startColor, @endColor, @deg |
Create a cross-browser directional background gradient |
.#gradient > .vertical-three-colors() |
@startColor, @midColor, @colorStop, @endColor |
Create a cross-browser three-color background gradient |
.#gradient > .radial() |
@innerColor, @outerColor |
Create a cross-browser radial background gradient |
.#gradient > .striped() |
@color, @angle |
Create a cross-browser striped background gradient |
.#gradientBar() |
@primaryColor, @secondaryColor |
Used for buttons to assign a gradient and slightly darker border |
Compiling Bootstrap with LESS
Tools for compiling
Node with makefile
Install the LESS command line compiler with npm by running the following command:
$ npm install less
Once installed just run make from the root of your bootstrap directory and you're all set.
Additionally, if you have watchr installed, you may run make watch to have bootstrap automatically rebuilt every time you edit a file in the bootstrap lib (this isn't required, just a convenience method).
Command line
Install the LESS command line tool via Node and run the following command:
$ lessc ./lib/bootstrap.less > bootstrap.css
Be sure to include --compress in that command if you're trying to save some bytes!
Javascript
Download the latest Less.js and include the path to it (and Bootstrap) in the <head>.
<link rel="stylesheet/less" href="/path/to/bootstrap.less"> <script src="/path/to/less.js"></script>
To recompile the .less files, just save them and reload your page. Less.js compiles them and stores them in local storage.
Unofficial Mac app
The unofficial Mac app watches directories of .less files and compiles the code to local files after every save of a watched .less file.
If you like, you can toggle preferences in the app for automatic minifying and which directory the compiled files end up in.
More Mac apps
Crunch
Crunch is a great looking LESS editor and compiler built on Adobe Air.
CodeKit
Created by the same guy as the unofficial Mac app, CodeKit is a Mac app that compiles LESS, SASS, Stylus, and CoffeeScript.
Simpless
Mac, Linux, and PC app for drag and drop compiling of LESS files. Plus, the source code is on GitHub.