Customize and extend Bootstrap with LESS, a CSS preprocessor, to take advantage of the variables, mixins, and more used to build Bootstrap's CSS.
Bootstrap is made with LESS at its core, a dynamic stylesheet language created by our good friend, Alexis Sellier. It makes developing systems-based CSS faster, easier, and more fun.
As an extension of CSS, LESS includes variables, mixins for reusable snippets of code, operations for simple math, nesting, and even color functions.
Visit the official website at http://lesscss.org to learn more.
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.
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.
Make your grid, leading, and more super flexible by doing the math on the fly with operations. Multiply, divide, add, and subtract your way to CSS sanity.
@bodyBackground |
@white |
Page background color | |
@textColor |
@grayDark |
Default text color for entire body, headings, and more | |
@linkColor |
#08c |
Default link text color | |
@linkColorHover |
darken(@linkColor, 15%) |
Default link text hover color |
@gridColumns |
12 |
@gridColumnWidth |
60px |
@gridGutterWidth |
20px |
@fluidGridColumnWidth |
6.382978723% |
@fluidGridGutterWidth |
2.127659574% |
@sansFontFamily |
"Helvetica Neue", Helvetica, Arial, sans-serif | |
@serifFontFamily |
Georgia, "Times New Roman", Times, serif |
|
@monoFontFamily |
Menlo, Monaco, "Courier New", monospace | |
@baseFontSize |
13px | Must be pixels |
@baseFontFamily |
@sansFontFamily |
|
@baseLineHeight |
18px | Must be pixels |
@altFontFamily |
@serifFontFamily |
|
@headingsFontFamily |
inherit |
|
@headingsFontWeight |
bold |
|
@headingsColor |
inherit |
@tableBackground |
transparent |
@tableBackgroundAccent |
#f9f9f9 |
@tableBackgroundHover |
#f5f5f5 |
@tableBorder |
#ddd |
@black |
#000 | |
@grayDarker |
#222 | |
@grayDark |
#333 | |
@gray |
#555 | |
@grayLight |
#999 | |
@grayLighter |
#eee | |
@white |
#fff |
@blue |
#049cdb | |
@green |
#46a546 | |
@red |
#9d261d | |
@yellow |
#ffc40d | |
@orange |
#f89406 | |
@pink |
#c3325f | |
@purple |
#7a43b6 |
@btnBackground |
@white |
|
@btnBackgroundHighlight |
darken(@white, 10%) |
|
@btnBorder |
darken(@white, 20%) |
|
@btnPrimaryBackground |
@linkColor |
|
@btnPrimaryBackgroundHighlight |
spin(@btnPrimaryBackground, 15%) |
|
@btnInfoBackground |
#5bc0de |
|
@btnInfoBackgroundHighlight |
#2f96b4 |
|
@btnSuccessBackground |
#62c462 |
|
@btnSuccessBackgroundHighlight |
51a351 |
|
@btnWarningBackground |
lighten(@orange, 15%) |
|
@btnWarningBackgroundHighlight |
@orange |
|
@btnDangerBackground |
#ee5f5b |
|
@btnDangerBackgroundHighlight |
#bd362f |
|
@btnInverseBackground |
@gray |
|
@btnInverseBackgroundHighlight |
@grayDarker |
@placeholderText |
@grayLight |
@inputBackground |
@white |
@inputBorder |
#ccc |
@inputBorderRadius |
3px |
@inputDisabledBackground |
@grayLighter |
@formActionsBackground |
#f5f5f5 |
@warningText |
#c09853 | |
@warningBackground |
#f3edd2 | |
@errorText |
#b94a48 | |
@errorBackground |
#f2dede | |
@successText |
#468847 | |
@successBackground |
#dff0d8 | |
@infoText |
#3a87ad | |
@infoBackground |
#d9edf7 |
@navbarHeight |
40px | |
@navbarBackground |
@grayDarker |
|
@navbarBackgroundHighlight |
@grayDark |
|
@navbarText |
@grayLight |
|
@navbarLinkColor |
@grayLight |
|
@navbarLinkColorHover |
@white |
|
@navbarLinkColorActive |
@navbarLinkColorHover |
|
@navbarLinkBackgroundHover |
transparent |
|
@navbarLinkBackgroundActive |
@navbarBackground |
|
@navbarSearchBackground |
lighten(@navbarBackground, 25%) |
|
@navbarSearchBackgroundFocus |
@white |
|
@navbarSearchBorder |
darken(@navbarSearchBackground, 30%) |
|
@navbarSearchPlaceholderColor |
#ccc |
|
@navbarBrandColor |
@navbarLinkColor |
@dropdownBackground |
@white |
@dropdownBorder |
rgba(0,0,0,.2) |
@dropdownLinkColor |
@grayDark |
@dropdownLinkColorHover |
@white |
@dropdownLinkBackgroundHover |
@linkColor |
@dropdownDividerTop |
#e5e5e5 |
@dropdownDividerBottom |
@white |
@heroUnitBackground |
@grayLighter |
|
@heroUnitHeadingColor |
inherit |
|
@heroUnitLeadColor |
inhereit |
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(); }
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); }
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.
Mixin | Parameters | Usage |
---|---|---|
.clearfix() |
none | Add to any parent to clear floats within |
.tab-focus() |
none | Apply the Webkit focus style and round Firefox outline |
.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 @width |
Quickly set the height and width on one line |
.square() |
@size |
Builds on .size() to set the width and height as same value |
.opacity() |
@opacity |
Set, in whole numbers, the opacity percentage (e.g., "50" or "75") |
Mixin | Parameters | Usage |
---|---|---|
.placeholder() |
@color: @placeholderText |
Set the placeholder text color for inputs |
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 |
Mixin | Parameters | Usage |
---|---|---|
.container-fixed() |
none | Create a horizontally centered container for holding your content |
#grid > .core() |
@gridColumnWidth, @gridGutterWidth |
Generate a pixel grid system (container, row, and columns) with n columns and x pixel wide gutter |
#grid > .fluid() |
@fluidGridColumnWidth, @fluidGridGutterWidth |
Generate a percent grid system with n columns and x % wide gutter |
#grid > .input() |
@gridColumnWidth, @gridGutterWidth |
Generate the pixel grid system for input elements, accounting for padding and borders |
.makeColumn |
@columns: 1, @offset: 0 |
Turn any div into a grid column without the .span* classes |
Mixin | Parameters | Usage |
---|---|---|
.border-radius() |
@radius |
Round the corners of an element. Can be a single value or four space-separated values |
.box-shadow() |
@shadow |
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 its original size |
.translate() |
@x, @y |
Move an element on the x and y planes |
.background-clip() |
@clip |
Crop the background 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 |
.backface-visibility() |
@visibility: visible |
Prevent flickering of content when using CSS 3D transforms |
.resizable() |
@direction: both |
Make any element resizable on the right and bottom |
.content-columns() |
@columnCount, @columnGap: @gridGutterWidth |
Make the content of any element use CSS3 columns |
.hyphens() |
@mode: auto |
CSS3 hyphenation when you want it (includes word-wrap: break-word ) |
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 |
Install the LESS command line compiler, JSHint, Recess, and uglify-js globally with npm by running the following command:
$ npm install -g less jshint recess uglify-js
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).
Install the LESS command line tool via Node and run the following command:
$ lessc ./less/bootstrap.less > bootstrap.css
Be sure to include --compress
in that command if you're trying to save some bytes!
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.
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.
Crunch is a great looking LESS editor and compiler built on Adobe Air.
Created by the same guy as the unofficial Mac app, CodeKit is a Mac app that compiles LESS, SASS, Stylus, and CoffeeScript.
Mac, Linux, and PC app for drag and drop compiling of LESS files. Plus, the source code is on GitHub.