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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="Less extends CSS with dynamic behavior such as variables, mixins, operations and functions. Less runs on both the server-side (with Node.js and Rhino) or client-side (modern browsers only).
">
<meta name="author" content="The Core Less Team">
<title>
Getting started | Less.js
</title>
<link href="https://fonts.googleapis.com/css?family=Noto+Serif|Oxygen" rel="stylesheet">
<!-- Algolia DocSearch styles -->
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<!-- HTML5 shim and Respond.js IE8 support of HTML5 elements and media queries -->
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<div>
<img src="public/img/less_logo.png" style="max-width: 264px">
<h3>It's CSS, with just a little more.</h3>
<p>Use with Node.js:</p>
<code>npm install -g less</code><br>
<code>> lessc styles.less styles.css</code>
<br><br>
<p>Or the browser:</p>
<code><link rel="stylesheet/less" type="text/css" href="styles.less" /></code><br>
<code><script src="<a href="https://cdn.jsdelivr.net/npm/less">https://cdn.jsdelivr.net/npm/less</a>" ></script></code><br>
<br><br>
<p>Or try <code><a href="http://lesscss.org/less-preview">the online playground</a></code> ! 🆕</p>
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View the <a href="https://github.com/less/less.js/blob/master/CHANGELOG.md">Less.js changelog</a>
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<li><a href="#nesting">Nesting</a><ul class="nav"><li><a href="#nesting-nested-at-rules-and-bubbling">Nested At-Rules and Bubbling</a></li></ul></li>
<li><a href="#operations">Operations</a><ul class="nav"><li><a href="#operations-calc-exception">calc() exception</a></li></ul></li>
<li><a href="#escaping">Escaping</a></li>
<li><a href="#functions">Functions</a></li>
<li><a href="#namespaces-and-accessors">Namespaces and Accessors</a></li>
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<h1 id="overview" class="docs-heading"><span class="anchor-target" id="overview"></span>
<a href="#overview" name="overview" class="anchor glyphicon glyphicon-link"></a>Overview</h1>
</div>
<blockquote>
<p>Less (which stands for Leaner Style Sheets) is a backwards-compatible language extension for CSS. This is the official documentation for Less, the language and Less.js, the JavaScript tool that converts your Less styles to CSS styles.</p>
</blockquote>
<p>Because Less looks just like CSS, learning it is a breeze. Less only makes a few convenient additions to the CSS language, which is one of the reasons it can be learned so quickly.</p>
<ul>
<li><em>For detailed documentation on Less language features, see <a href="../features/">Features</a></em></li>
<li><em>For a list of Less Built-in functions, see <a href="../functions/">Functions</a></em></li>
<li><em>For detailed usage instructions, see <a href="../usage/">Using Less.js</a></em></li>
<li><em>For third-party tools for Less, see <a href="../tools/">Tools</a></em></li>
</ul>
<p>What does Less add to CSS? Here's a quick overview of features.</p>
<h1 id="variables" class="docs-heading"><span class="anchor-target" id="variables"></span>
<a href="#variables" name="variables" class="anchor glyphicon glyphicon-link"></a>Variables</h1>
<p>These are pretty self-explanatory:</p>
<pre><code class="lang-less"><span class="hljs-variable">@width:</span> <span class="hljs-number">10px</span>;
<span class="hljs-variable">@height:</span> <span class="hljs-variable">@width</span> + <span class="hljs-number">10px</span>;
<span class="hljs-id">#header</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-variable">@width</span>;
<span class="hljs-attribute">height</span>: <span class="hljs-variable">@height</span>;
}
</code></pre>
<p>Outputs:</p>
<pre><code class="lang-css"><span class="hljs-id">#header</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-number">10px</span>;
<span class="hljs-attribute">height</span>: <span class="hljs-number">20px</span>;
}
</code></pre>
<p><strong><a href="../features/#variables-feature">Learn More About Variables</a></strong> </p>
<h1 id="mixins" class="docs-heading"><span class="anchor-target" id="mixins"></span>
<a href="#mixins" name="mixins" class="anchor glyphicon glyphicon-link"></a>Mixins</h1>
<p>Mixins are a way of including ("mixing in") a bunch of properties from one rule-set into another rule-set. So say we have the following class:</p>
<pre><code class="lang-css"><span class="hljs-class">.bordered</span> {
<span class="hljs-attribute">border-top</span>: dotted <span class="hljs-number">1px</span> black;
<span class="hljs-attribute">border-bottom</span>: solid <span class="hljs-number">2px</span> black;
}
</code></pre>
<p>And we want to use these properties inside other rule-sets. Well, we just have to drop in the name of the class where we want the properties, like so:</p>
<pre><code class="lang-less"><span class="hljs-id">#menu</span> <span class="hljs-tag">a</span> {
<span class="hljs-attribute">color</span>: <span class="hljs-hexcolor">#111</span>;
<span class="hljs-class">.bordered</span>();
}
<span class="hljs-class">.post</span> <span class="hljs-tag">a</span> {
<span class="hljs-attribute">color</span>: red;
<span class="hljs-class">.bordered</span>();
}
</code></pre>
<p>The properties of the <code>.bordered</code> class will now appear in both <code>#menu a</code> and <code>.post a</code>. (Note that you can also use <code>#ids</code> as mixins.)</p>
<p><strong><a href="../features/#mixins-feature">Learn More About Mixins</a></strong> </p>
<h1 id="nesting" class="docs-heading"><span class="anchor-target" id="nesting"></span>
<a href="#nesting" name="nesting" class="anchor glyphicon glyphicon-link"></a>Nesting</h1>
<p>Less gives you the ability to use nesting instead of, or in combination with cascading. Let's say we have the following CSS:</p>
<pre><code class="lang-css"><span class="hljs-id">#header</span> {
<span class="hljs-attribute">color</span>: black;
}
<span class="hljs-id">#header</span> <span class="hljs-class">.navigation</span> {
<span class="hljs-attribute">font-size</span>: <span class="hljs-number">12px</span>;
}
<span class="hljs-id">#header</span> <span class="hljs-class">.logo</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-number">300px</span>;
}
</code></pre>
<p>In Less, we can also write it this way:</p>
<pre><code class="lang-less"><span class="hljs-id">#header</span> {
<span class="hljs-attribute">color</span>: black;
<span class="hljs-class">.navigation</span> {
<span class="hljs-attribute">font-size</span>: <span class="hljs-number">12px</span>;
}
<span class="hljs-class">.logo</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-number">300px</span>;
}
}
</code></pre>
<p>The resulting code is more concise, and mimics the structure of your HTML.</p>
<p>You can also bundle pseudo-selectors with your mixins using this method. Here's the classic clearfix hack, rewritten as a mixin (<code>&</code> represents the current selector parent):</p>
<pre><code class="lang-less"><span class="hljs-class">.clearfix</span> {
<span class="hljs-attribute">display</span>: block;
<span class="hljs-attribute">zoom</span>: <span class="hljs-number">1</span>;
<span class="hljs-keyword">&</span><span class="hljs-pseudo">:after</span> {
<span class="hljs-attribute">content</span>: <span class="hljs-string">" "</span>;
<span class="hljs-attribute">display</span>: block;
<span class="hljs-attribute">font-size</span>: <span class="hljs-number">0</span>;
<span class="hljs-attribute">height</span>: <span class="hljs-number">0</span>;
<span class="hljs-attribute">clear</span>: both;
<span class="hljs-attribute">visibility</span>: hidden;
}
}
</code></pre>
<p><strong><a href="../features/#parent-selectors-feature">Learn More About Parent Selectors</a></strong> </p>
<h2 id="nesting-nested-at-rules-and-bubbling" class="docs-heading"><span class="anchor-target" id="nesting-nested-at-rules-and-bubbling"></span>
<a href="#nesting-nested-at-rules-and-bubbling" name="nesting-nested-at-rules-and-bubbling" class="anchor glyphicon glyphicon-link"></a>Nested At-Rules and Bubbling</h2>
<p>At-rules such as <code>@media</code> or <code>@supports</code> can be nested in the same way as selectors. The at-rule is placed on top and relative order against other elements inside the same ruleset remains unchanged. This is called bubbling.</p>
<pre><code class="lang-less"><span class="hljs-class">.component</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-number">300px</span>;
<span class="hljs-at_rule">@media</span> (min-width: <span class="hljs-number">768px</span>) {
<span class="hljs-attribute">width</span>: <span class="hljs-number">600px</span>;
<span class="hljs-at_rule">@media</span> (min-resolution: <span class="hljs-number">192dpi</span>) {
<span class="hljs-attribute">background-image</span>: url(<span class="hljs-string">/img/retina2x.png</span>);
}
}
<span class="hljs-at_rule">@media</span> (min-width: <span class="hljs-number">1280px</span>) {
<span class="hljs-attribute">width</span>: <span class="hljs-number">800px</span>;
}
}
</code></pre>
<p>outputs:</p>
<pre><code class="lang-css"><span class="hljs-class">.component</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-number">300px</span>;
}
<span class="hljs-at_rule">@media</span> (min-width: <span class="hljs-number">768px</span>) {
<span class="hljs-class">.component</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-number">600px</span>;
}
}
<span class="hljs-at_rule">@media</span> (min-width: <span class="hljs-number">768px</span>) and (min-resolution: <span class="hljs-number">192dpi</span>) {
<span class="hljs-class">.component</span> {
<span class="hljs-attribute">background-image</span>: url(<span class="hljs-string">/img/retina2x.png</span>);
}
}
<span class="hljs-at_rule">@media</span> (min-width: <span class="hljs-number">1280px</span>) {
<span class="hljs-class">.component</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-number">800px</span>;
}
}
</code></pre>
<h1 id="operations" class="docs-heading"><span class="anchor-target" id="operations"></span>
<a href="#operations" name="operations" class="anchor glyphicon glyphicon-link"></a>Operations</h1>
<p>Arithmetical operations <code>+</code>, <code>-</code>, <code>*</code>, <code>/</code> can operate on any number, color or variable. If it is possible, mathematical operations take units into account and convert numbers before adding, subtracting or comparing them. The result has leftmost explicitly stated unit type. If the conversion is impossible or not meaningful, units are ignored. Example of impossible conversion: px to cm or rad to %.</p>
<pre><code class="lang-less"><span class="hljs-comment">// numbers are converted into the same units</span>
<span class="hljs-variable">@conversion-1:</span> <span class="hljs-number">5cm</span> + <span class="hljs-number">10mm</span>; <span class="hljs-comment">// result is 6cm</span>
<span class="hljs-variable">@conversion-2:</span> <span class="hljs-number">2</span> - <span class="hljs-number">3cm</span> - <span class="hljs-number">5mm</span>; <span class="hljs-comment">// result is -1.5cm</span>
<span class="hljs-comment">// conversion is impossible</span>
<span class="hljs-variable">@incompatible-units:</span> <span class="hljs-number">2</span> + <span class="hljs-number">5px</span> - <span class="hljs-number">3cm</span>; <span class="hljs-comment">// result is 4px</span>
<span class="hljs-comment">// example with variables</span>
<span class="hljs-variable">@base:</span> <span class="hljs-number">5%</span>;
<span class="hljs-variable">@filler:</span> <span class="hljs-variable">@base</span> * <span class="hljs-number">2</span>; <span class="hljs-comment">// result is 10%</span>
<span class="hljs-variable">@other:</span> <span class="hljs-variable">@base</span> + <span class="hljs-variable">@filler</span>; <span class="hljs-comment">// result is 15%</span>
</code></pre>
<p>Multiplication and division do not convert numbers. It would not be meaningful in most cases - a length multiplied by a length gives an area and css does not support specifying areas. Less will operate on numbers as they are and assign explicitly stated unit type to the result.</p>
<pre><code class="lang-less"><span class="hljs-variable">@base:</span> <span class="hljs-number">2cm</span> * <span class="hljs-number">3mm</span>; <span class="hljs-comment">// result is 6cm</span>
</code></pre>
<p>You can also do arithmetic on colors:</p>
<pre><code class="lang-less"><span class="hljs-variable">@color:</span> (<span class="hljs-hexcolor">#224488</span> / <span class="hljs-number">2</span>); <span class="hljs-comment">// result is #112244</span>
<span class="hljs-attribute">background-color</span>: <span class="hljs-hexcolor">#112244</span> + <span class="hljs-hexcolor">#111</span>; <span class="hljs-comment">// result is #223355</span>
</code></pre>
<p>However, you may find Less's <a href="../functions/#color-operations">Color Functions</a> more useful.</p>
<p>From 4.0, No division is performed outside of parens using <code>/</code> operator.</p>
<pre><code class="lang-less"><span class="hljs-variable">@color:</span> <span class="hljs-hexcolor">#222</span> / <span class="hljs-number">2</span>; <span class="hljs-comment">// results in `#222 / 2`, not #111</span>
<span class="hljs-attribute">background-color</span>: (<span class="hljs-hexcolor">#FFFFFF</span> / <span class="hljs-number">16</span>); <span class="hljs-comment">//results is #101010</span>
</code></pre>
<p>You can change <a href="../usage/#less-options-math">Math</a> setting, if you want to make it always work, but not recommended.</p>
<h2 id="operations-calc-exception" class="docs-heading"><span class="anchor-target" id="operations-calc-exception"></span>
<a href="#operations-calc-exception" name="operations-calc-exception" class="anchor glyphicon glyphicon-link"></a>calc() exception</h2>
<p><em>Released <a href="https://github.com/less/less.js/blob/master/CHANGELOG.md">v3.0.0</a></em></p>
<p>For CSS compatibility, <code>calc()</code> does not evaluate math expressions, but will evaluate variables
and math in nested functions.</p>
<pre><code class="lang-less"><span class="hljs-variable">@var:</span> <span class="hljs-number">50vh</span>/<span class="hljs-number">2</span>;
<span class="hljs-attribute">width</span>: <span class="hljs-function">calc</span>(<span class="hljs-number">50%</span> + (<span class="hljs-variable">@var</span> - <span class="hljs-number">20px</span>)); <span class="hljs-comment">// result is calc(50% + (25vh - 20px))</span>
</code></pre>
<h1 id="escaping" class="docs-heading"><span class="anchor-target" id="escaping"></span>
<a href="#escaping" name="escaping" class="anchor glyphicon glyphicon-link"></a>Escaping</h1>
<p>Escaping allows you to use any arbitrary string as property or variable value. Anything inside <code>~"anything"</code> or <code>~'anything'</code> is used as is with no changes except <a href="../features/#variables-feature-variable-interpolation">interpolation</a>.</p>
<pre><code class="lang-less"><span class="hljs-variable">@min768:</span> <span class="hljs-string">~"(min-width: 768px)"</span>;
<span class="hljs-class">.element</span> {
<span class="hljs-at_rule">@media</span> <span class="hljs-variable">@min768</span> {
<span class="hljs-attribute">font-size</span>: <span class="hljs-number">1.2rem</span>;
}
}
</code></pre>
<p>results in:</p>
<pre><code class="lang-less"><span class="hljs-at_rule">@media</span> (min-width: <span class="hljs-number">768px</span>) {
<span class="hljs-class">.element</span> {
<span class="hljs-attribute">font-size</span>: <span class="hljs-number">1.2rem</span>;
}
}
</code></pre>
<p>Note, as of Less 3.5, you can simply write:</p>
<pre><code class="lang-less"><span class="hljs-variable">@min768:</span> (min-width: <span class="hljs-number">768px</span>);
<span class="hljs-class">.element</span> {
<span class="hljs-at_rule">@media</span> <span class="hljs-variable">@min768</span> {
<span class="hljs-attribute">font-size</span>: <span class="hljs-number">1.2rem</span>;
}
}
</code></pre>
<p>In 3.5+, many cases previously requiring "quote-escaping" are not needed.</p>
<h1 id="functions" class="docs-heading"><span class="anchor-target" id="functions"></span>
<a href="#functions" name="functions" class="anchor glyphicon glyphicon-link"></a>Functions</h1>
<p>Less provides a variety of functions which transform colors, manipulate strings and do maths. They are documented fully in the <a href="../functions/">function reference</a>.</p>
<p>Using them is pretty straightforward. The following example uses percentage to convert 0.5 to 50%, increases the saturation of a base color by 5% and then sets the background color to one that is lightened by 25% and spun by 8 degrees:</p>
<pre><code class="lang-less"><span class="hljs-variable">@base:</span> <span class="hljs-hexcolor">#f04615</span>;
<span class="hljs-variable">@width:</span> <span class="hljs-number">0.5</span>;
<span class="hljs-class">.class</span> {
<span class="hljs-attribute">width</span>: <span class="hljs-function">percentage</span>(<span class="hljs-variable">@width</span>); <span class="hljs-comment">// returns `50%`</span>
<span class="hljs-attribute">color</span>: <span class="hljs-function">saturate</span>(<span class="hljs-variable">@base</span>, <span class="hljs-number">5%</span>);
<span class="hljs-attribute">background-color</span>: <span class="hljs-function">spin</span>(<span class="hljs-function">lighten</span>(<span class="hljs-variable">@base</span>, <span class="hljs-number">25%</span>), <span class="hljs-number">8</span>);
}
</code></pre>
<p><strong><a href="../functions/">See: Function Reference</a></strong> </p>
<h1 id="namespaces-and-accessors" class="docs-heading"><span class="anchor-target" id="namespaces-and-accessors"></span>
<a href="#namespaces-and-accessors" name="namespaces-and-accessors" class="anchor glyphicon glyphicon-link"></a>Namespaces and Accessors</h1>
<p>(Not to be confused with <a href="http://www.w3.org/TR/css3-namespace/">CSS <code>@namespace</code></a> or <a href="http://www.w3.org/TR/css3-selectors/#typenmsp">namespace selectors</a>).</p>
<p>Sometimes, you may want to group your mixins, for organizational purposes, or just to offer some encapsulation. You can do this pretty intuitively in Less. Say you want to bundle some mixins and variables under <code>#bundle</code>, for later reuse or distributing:</p>
<pre><code class="lang-less"><span class="hljs-id">#bundle</span>() {
<span class="hljs-class">.button</span> {
<span class="hljs-attribute">display</span>: block;
<span class="hljs-attribute">border</span>: <span class="hljs-number">1px</span> solid black;
<span class="hljs-attribute">background-color</span>: grey;
<span class="hljs-keyword">&</span><span class="hljs-pseudo">:hover</span> {
<span class="hljs-attribute">background-color</span>: white;
}
}
<span class="hljs-class">.tab</span> { ... }
<span class="hljs-class">.citation</span> { ... }
}
</code></pre>
<p>Now if we want to mixin the <code>.button</code> class in our <code>#header a</code>, we can do:</p>
<pre><code class="lang-less"><span class="hljs-id">#header</span> <span class="hljs-tag">a</span> {
<span class="hljs-attribute">color</span>: orange;
<span class="hljs-id">#bundle</span><span class="hljs-class">.button</span>(); <span class="hljs-comment">// can also be written as #bundle > .button</span>
}
</code></pre>
<p>Note: append <code>()</code> to your namespace (e.g. <code>#bundle()</code>) if you don't want it to appear in your CSS output i.e. <code>#bundle .tab</code>.</p>
<h1 id="maps" class="docs-heading"><span class="anchor-target" id="maps"></span>
<a href="#maps" name="maps" class="anchor glyphicon glyphicon-link"></a>Maps</h1>
<p>As of Less 3.5, you can also use mixins and rulesets as maps of values.</p>
<pre><code class="lang-less"><span class="hljs-id">#colors</span>() {
<span class="hljs-attribute">primary</span>: blue;
<span class="hljs-attribute">secondary</span>: green;
}
<span class="hljs-class">.button</span> {
<span class="hljs-attribute">color</span>: #colors[primary];
<span class="hljs-attribute">border</span>: <span class="hljs-number">1px</span> solid #colors[secondary];
}
</code></pre>
<p>This outputs, as expected:</p>
<pre><code class="lang-css"><span class="hljs-class">.button</span> {
<span class="hljs-attribute">color</span>: blue;
<span class="hljs-attribute">border</span>: <span class="hljs-number">1px</span> solid green;
}
</code></pre>
<p><strong><a href="../features/#maps-feature">See also: Maps</a></strong></p>
<h1 id="scope" class="docs-heading"><span class="anchor-target" id="scope"></span>
<a href="#scope" name="scope" class="anchor glyphicon glyphicon-link"></a>Scope</h1>
<p>Scope in Less is very similar to that of CSS. Variables and mixins are first looked for locally, and if they aren't found, it's inherited from the "parent" scope.</p>
<pre><code class="lang-less"><span class="hljs-variable">@var:</span> red;
<span class="hljs-id">#page</span> {
<span class="hljs-variable">@var:</span> white;
<span class="hljs-id">#header</span> {
<span class="hljs-attribute">color</span>: <span class="hljs-variable">@var</span>; <span class="hljs-comment">// white</span>
}
}
</code></pre>
<p>Like CSS custom properties, mixin and variable definitions do not have to be placed before a line where they are referenced. So the following Less code is identical to the previous example:</p>
<pre><code class="lang-less"><span class="hljs-variable">@var:</span> red;
<span class="hljs-id">#page</span> {
<span class="hljs-id">#header</span> {
<span class="hljs-attribute">color</span>: <span class="hljs-variable">@var</span>; <span class="hljs-comment">// white</span>
}
<span class="hljs-variable">@var:</span> white;
}
</code></pre>
<p><strong><a href="../features/#variables-feature-lazy-loading">See also: Lazy Loading</a></strong></p>
<h1 id="comments" class="docs-heading"><span class="anchor-target" id="comments"></span>
<a href="#comments" name="comments" class="anchor glyphicon glyphicon-link"></a>Comments</h1>
<p>Both block-style and inline comments may be used:</p>
<pre><code class="lang-less"><span class="hljs-comment">/* One heck of a block
* style comment! */</span>
<span class="hljs-variable">@var:</span> red;
<span class="hljs-comment">// Get in line!</span>
<span class="hljs-variable">@var:</span> white;
</code></pre>
<h1 id="importing" class="docs-heading"><span class="anchor-target" id="importing"></span>
<a href="#importing" name="importing" class="anchor glyphicon glyphicon-link"></a>Importing</h1>
<p>Importing works pretty much as expected. You can import a <code>.less</code> file, and all the variables in it will be available. The extension is optionally specified for <code>.less</code> files.</p>
<pre><code class="lang-css"><span class="hljs-at_rule">@import</span> <span class="hljs-string">"library"</span>; <span class="hljs-comment">// library.less</span>
<span class="hljs-at_rule">@import</span> <span class="hljs-string">"typo.css"</span>;
</code></pre>
<p><strong><a href="../features/#imports-feature">Learn More About Imports</a></strong> </p>
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