了解Bootstrap基础设施的关键部分，包括我们更好、更快、更强Web开发的方法。

HTML5 doctype

Bootstrap使用某些需要HTML5 doctype的HTML元素和CSS属性。在所有项目的开头包含它。

<!DOCTYPE html>
<html lang="en">
  ...
</html>

移动优先

在Bootstrap 2中，我们为框架的关键方面添加了可选的移动友好样式。在Bootstrap 3中，我们重写了项目，从一开始就是移动友好的。不是添加可选的移动样式，而是直接内置到核心中。事实上，Bootstrap是移动优先的。移动优先样式可以在整个库中找到，而不是在单独的文件中。

为了确保正确的渲染和触摸缩放，在<head>中添加视口meta标签。

<meta name="viewport" content="width=device-width, initial-scale=1">

您可以通过在视口meta标签中添加user-scalable=no来禁用移动设备上的缩放功能。这会禁用缩放，意味着用户只能滚动，并使您的网站感觉更像原生应用程序。总的来说，我们不建议在每个网站上使用这个，所以要谨慎使用！

<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">

排版和链接

Bootstrap设置基本的全局显示、排版和链接样式。具体来说，我们：

在body上设置background-color: #fff;
使用@font-family-base、@font-size-base和@line-height-base属性作为我们的排版基础
通过@link-color设置全局链接颜色，并仅在:hover上应用链接下划线

这些样式可以在scaffolding.less中找到。

Normalize.css

为了改善跨浏览器渲染，我们使用Normalize.css，这是Nicolas Gallagher和Jonathan Neal的项目。

容器

Bootstrap需要一个包含元素来包装网站内容并容纳我们的网格系统。您可以在项目中选择两种容器之一。请注意，由于padding等原因，两种容器都不能嵌套。

使用.container作为响应式固定宽度容器。

<div class="container">
  ...
</div>

使用.container-fluid作为全宽容器，跨越视口的整个宽度。

<div class="container-fluid">
  ...
</div>

Bootstrap包含一个响应式、移动优先的流体网格系统，随着设备或视口大小的增加，它会适当地扩展到12列。它包括用于简单布局选项的预定义类，以及用于生成更语义化布局的强大混合器。

介绍

网格系统用于通过一系列包含内容的行和列来创建页面布局。以下是Bootstrap网格系统的工作原理：

行必须放在.container（固定宽度）或.container-fluid（全宽）内，以获得正确的对齐和填充。
使用行来创建列的水平组。
内容应该放在列内，只有列可能是行的直接子元素。
预定义的网格类如.row和.col-xs-4可用于快速制作网格布局。Less混合器也可用于更语义化的布局。
列通过padding创建沟槽（列内容之间的间隙）。该填充通过.row上的负边距在行中为第一列和最后一列偏移。
负边距是下面示例缩进的原因。这是为了让网格列内的内容与非网格内容对齐。
网格列通过指定您希望跨越的12个可用列的数量来创建。例如，三个相等的列将使用三个.col-xs-4。
如果在单行中放置超过12列，每组额外的列将作为一个单元换行到新行。
网格类适用于屏幕宽度大于或等于断点大小的设备，并覆盖针对较小设备的网格类。因此，例如，将任何.col-md-*类应用到元素不仅会影响其在中等设备上的样式，如果没有.col-lg-*类，还会影响其在大型设备上的样式。

查看示例以了解如何将这些原则应用到您的代码中。

媒体查询

我们在Less文件中使用以下媒体查询来创建网格系统中的关键断点。

/* Extra small devices (phones, less than 768px) */
/* No media query since this is the default in Bootstrap */

/* Small devices (tablets, 768px and up) */
@media (min-width: @screen-sm-min) { ... }

/* Medium devices (desktops, 992px and up) */
@media (min-width: @screen-md-min) { ... }

/* Large devices (large desktops, 1200px and up) */
@media (min-width: @screen-lg-min) { ... }

我们偶尔扩展这些媒体查询以包含max-width，将CSS限制在更窄的设备集上。

@media (max-width: @screen-xs-max) { ... }
@media (min-width: @screen-sm-min) and (max-width: @screen-sm-max) { ... }
@media (min-width: @screen-md-min) and (max-width: @screen-md-max) { ... }
@media (min-width: @screen-lg-min) { ... }

网格选项

通过一个方便的表格查看Bootstrap网格系统的各个方面如何在多个设备上工作。

	超小设备手机 (<768px)	小设备平板 (≥768px)	中等设备桌面 (≥992px)	大设备桌面 (≥1200px)
网格行为	始终水平	开始时折叠，断点以上水平
容器宽度	无（自动）	750px	970px	1170px
类前缀	`.col-xs-`	`.col-sm-`	`.col-md-`	`.col-lg-`
列数	12
列宽度	自动	~62px	~81px	~97px
沟槽宽度	30px（列每侧15px）
可嵌套	是
偏移	是
列排序	是

示例：堆叠到水平

使用一组.col-md-*网格类，您可以创建一个基本的网格系统，它在移动设备和平板设备（超小到小范围）上开始时是堆叠的，然后在桌面（中等）设备上变为水平。将网格列放在任何.row中。

.col-md-1

.col-md-8

.col-md-4

.col-md-6

<div class="row">
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
  <div class="col-md-1">.col-md-1</div>
</div>
<div class="row">
  <div class="col-md-8">.col-md-8</div>
  <div class="col-md-4">.col-md-4</div>
</div>
<div class="row">
  <div class="col-md-4">.col-md-4</div>
  <div class="col-md-4">.col-md-4</div>
  <div class="col-md-4">.col-md-4</div>
</div>
<div class="row">
  <div class="col-md-6">.col-md-6</div>
  <div class="col-md-6">.col-md-6</div>
</div>

示例：流体容器

通过将最外层的.container更改为.container-fluid，将任何固定宽度的网格布局转换为全宽布局。

<div class="container-fluid">
  <div class="row">
    ...
  </div>
</div>

示例：移动和桌面

不希望您的列在较小设备上简单堆叠？通过向列添加.col-xs-*和.col-md-*来使用超小和中等设备网格类。查看下面的示例以更好地了解它的工作原理。

.col-xs-12 .col-md-8

.col-xs-6 .col-md-4

.col-xs-6

<!-- 通过在移动设备上使一个全宽另一个半宽来堆叠列 -->
<div class="row">
  <div class="col-xs-12 col-md-8">.col-xs-12 .col-md-8</div>
  <div class="col-xs-6 col-md-4">.col-xs-6 .col-md-4</div>
</div>

<!-- 列在移动设备上从50%宽开始，在桌面上增加到33.3%宽 -->
<div class="row">
  <div class="col-xs-6 col-md-4">.col-xs-6 .col-md-4</div>
  <div class="col-xs-6 col-md-4">.col-xs-6 .col-md-4</div>
  <div class="col-xs-6 col-md-4">.col-xs-6 .col-md-4</div>
</div>

<!-- 列在移动设备和桌面上始终是50%宽 -->
<div class="row">
  <div class="col-xs-6">.col-xs-6</div>
  <div class="col-xs-6">.col-xs-6</div>
</div>

示例：移动、平板、桌面

通过使用平板.col-sm-*类创建更动态和强大的布局来构建前面的示例。

.col-xs-12 .col-sm-6 .col-md-8

.col-xs-6 .col-md-4

.col-xs-6 .col-sm-4

<div class="row">
  <div class="col-xs-12 col-sm-6 col-md-8">.col-xs-12 .col-sm-6 .col-md-8</div>
  <div class="col-xs-6 col-md-4">.col-xs-6 .col-md-4</div>
</div>
<div class="row">
  <div class="col-xs-6 col-sm-4">.col-xs-6 .col-sm-4</div>
  <div class="col-xs-6 col-sm-4">.col-xs-6 .col-sm-4</div>
  <!-- 可选：如果XS列的内容高度不匹配，则清除它们 -->
  <div class="clearfix visible-xs-block"></div>
  <div class="col-xs-6 col-sm-4">.col-xs-6 .col-sm-4</div>
</div>

示例：列换行

如果在单行中放置超过12列，每组额外的列将作为一个单元换行到新行。

.col-xs-9

.col-xs-4
Since 9 + 4 = 13 > 12, this 4-column-wide div gets wrapped onto a new line as one contiguous unit.

.col-xs-6
Subsequent columns continue along the new line.

<div class="row">
  <div class="col-xs-9">.col-xs-9</div>
  <div class="col-xs-4">.col-xs-4<br>Since 9 + 4 = 13 &gt; 12, this 4-column-wide div gets wrapped onto a new line as one contiguous unit.</div>
  <div class="col-xs-6">.col-xs-6<br>Subsequent columns continue along the new line.</div>
</div>

响应式列重置

有了四个层级的网格，您肯定会遇到在某些断点处列没有正确清除的问题，因为一个比另一个高。要修复这个问题，请使用.clearfix和我们的响应式工具类的组合。

.col-xs-6 .col-sm-3
Resize your viewport or check it out on your phone for an example.

.col-xs-6 .col-sm-3

<div class="row">
  <div class="col-xs-6 col-sm-3">.col-xs-6 .col-sm-3</div>
  <div class="col-xs-6 col-sm-3">.col-xs-6 .col-sm-3</div>

  <!-- 仅为所需的视口添加额外的clearfix -->
  <div class="clearfix visible-xs-block"></div>

  <div class="col-xs-6 col-sm-3">.col-xs-6 .col-sm-3</div>
  <div class="col-xs-6 col-sm-3">.col-xs-6 .col-sm-3</div>
</div>

除了在响应式断点处清除列之外，您可能还需要重置偏移、推入或拉出。在网格示例中查看实际操作。

<div class="row">
  <div class="col-sm-5 col-md-6">.col-sm-5 .col-md-6</div>
  <div class="col-sm-5 col-sm-offset-2 col-md-6 col-md-offset-0">.col-sm-5 .col-sm-offset-2 .col-md-6 .col-md-offset-0</div>
</div>

<div class="row">
  <div class="col-sm-6 col-md-5 col-lg-6">.col-sm-6 .col-md-5 .col-lg-6</div>
  <div class="col-sm-6 col-md-5 col-md-offset-2 col-lg-6 col-lg-offset-0">.col-sm-6 .col-md-5 .col-md-offset-2 .col-lg-6 .col-lg-offset-0</div>
</div>

偏移列

使用.col-md-offset-*类将列向右移动。这些类通过*列增加列的左边距。例如，.col-md-offset-4将.col-md-4移动四列。

.col-md-4

.col-md-4 .col-md-offset-4

.col-md-3 .col-md-offset-3

.col-md-6 .col-md-offset-3

<div class="row">
  <div class="col-md-4">.col-md-4</div>
  <div class="col-md-4 col-md-offset-4">.col-md-4 .col-md-offset-4</div>
</div>
<div class="row">
  <div class="col-md-3 col-md-offset-3">.col-md-3 .col-md-offset-3</div>
  <div class="col-md-3 col-md-offset-3">.col-md-3 .col-md-offset-3</div>
</div>
<div class="row">
  <div class="col-md-6 col-md-offset-3">.col-md-6 .col-md-offset-3</div>
</div>

嵌套列

要在默认网格中嵌套内容，请在现有的.col-sm-*列内添加新的.row和一组.col-sm-*列。嵌套行应包含总计为12或更少的列集（不要求您使用所有12个可用列）。

Level 1: .col-sm-9

Level 2: .col-xs-8 .col-sm-6

Level 2: .col-xs-4 .col-sm-6

<div class="row">
  <div class="col-sm-9">
    Level 1: .col-sm-9
    <div class="row">
      <div class="col-xs-8 col-sm-6">
        Level 2: .col-xs-8 .col-sm-6
      </div>
      <div class="col-xs-4 col-sm-6">
        Level 2: .col-xs-4 .col-sm-6
      </div>
    </div>
  </div>
</div>

列排序

使用.col-md-push-*和.col-md-pull-*修饰符类轻松更改内置网格列的顺序。

.col-md-9 .col-md-push-3

.col-md-3 .col-md-pull-9

<div class="row">
  <div class="col-md-9 col-md-push-3">.col-md-9 .col-md-push-3</div>
  <div class="col-md-3 col-md-pull-9">.col-md-3 .col-md-pull-9</div>
</div>

Less混合器和变量

除了用于快速布局的预构建网格类之外，Bootstrap还包括Less变量和混合器，用于快速生成您自己的简单、语义化布局。

变量

变量确定列数、沟槽宽度和开始浮动列的媒体查询点。我们使用这些来生成上面记录的预定义网格类，以及下面列出的自定义混合器。

@grid-columns:              12;
@grid-gutter-width:         30px;
@grid-float-breakpoint:     768px;

混合器

混合器与网格变量结合使用，为单个网格列生成语义化CSS。

// 为一系列列创建包装器
.make-row(@gutter: @grid-gutter-width) {
  // 然后清除浮动的列
  .clearfix();

  @media (min-width: @screen-sm-min) {
    margin-left:  (@gutter / -2);
    margin-right: (@gutter / -2);
  }

  // 负边距嵌套行以对齐列的内容
  .row {
    margin-left:  (@gutter / -2);
    margin-right: (@gutter / -2);
  }
}

// 生成超小列
.make-xs-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  // Prevent columns from collapsing when empty
  min-height: 1px;
  // Inner gutter via padding
  padding-left:  (@gutter / 2);
  padding-right: (@gutter / 2);

  // Calculate width based on number of columns available
  @media (min-width: @grid-float-breakpoint) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}

// Generate the small columns
.make-sm-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  // Prevent columns from collapsing when empty
  min-height: 1px;
  // Inner gutter via padding
  padding-left:  (@gutter / 2);
  padding-right: (@gutter / 2);

  // Calculate width based on number of columns available
  @media (min-width: @screen-sm-min) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}

// Generate the small column offsets
.make-sm-column-offset(@columns) {
  @media (min-width: @screen-sm-min) {
    margin-left: percentage((@columns / @grid-columns));
  }
}
.make-sm-column-push(@columns) {
  @media (min-width: @screen-sm-min) {
    left: percentage((@columns / @grid-columns));
  }
}
.make-sm-column-pull(@columns) {
  @media (min-width: @screen-sm-min) {
    right: percentage((@columns / @grid-columns));
  }
}

// Generate the medium columns
.make-md-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  // Prevent columns from collapsing when empty
  min-height: 1px;
  // Inner gutter via padding
  padding-left:  (@gutter / 2);
  padding-right: (@gutter / 2);

  // Calculate width based on number of columns available
  @media (min-width: @screen-md-min) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}

// Generate the medium column offsets
.make-md-column-offset(@columns) {
  @media (min-width: @screen-md-min) {
    margin-left: percentage((@columns / @grid-columns));
  }
}
.make-md-column-push(@columns) {
  @media (min-width: @screen-md-min) {
    left: percentage((@columns / @grid-columns));
  }
}
.make-md-column-pull(@columns) {
  @media (min-width: @screen-md-min) {
    right: percentage((@columns / @grid-columns));
  }
}

// Generate the large columns
.make-lg-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  // Prevent columns from collapsing when empty
  min-height: 1px;
  // Inner gutter via padding
  padding-left:  (@gutter / 2);
  padding-right: (@gutter / 2);

  // Calculate width based on number of columns available
  @media (min-width: @screen-lg-min) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}

// Generate the large column offsets
.make-lg-column-offset(@columns) {
  @media (min-width: @screen-lg-min) {
    margin-left: percentage((@columns / @grid-columns));
  }
}
.make-lg-column-push(@columns) {
  @media (min-width: @screen-lg-min) {
    left: percentage((@columns / @grid-columns));
  }
}
.make-lg-column-pull(@columns) {
  @media (min-width: @screen-lg-min) {
    right: percentage((@columns / @grid-columns));
  }
}

Example usage

You can modify the variables to your own custom values, or just use the mixins with their default values. Here's an example of using the default settings to create a two-column layout with a gap between.

.wrapper {
  .make-row();
}
.content-main {
  .make-lg-column(8);
}
.content-secondary {
  .make-lg-column(3);
  .make-lg-column-offset(1);
}

<div class="wrapper">
  <div class="content-main">...</div>
  <div class="content-secondary">...</div>
</div>

标题

所有HTML标题，从<h1>到<h6>，都可用。.h1到.h6类也可用，当您想要匹配标题的字体样式但仍然希望文本内联显示时。

h1. Bootstrap heading	Semibold 36px
h2. Bootstrap heading	Semibold 30px
h3. Bootstrap heading	Semibold 24px
h4. Bootstrap heading	Semibold 18px
h5. Bootstrap heading	Semibold 14px
h6. Bootstrap heading	Semibold 12px

<h1>h1. Bootstrap heading</h1>
<h2>h2. Bootstrap heading</h2>
<h3>h3. Bootstrap heading</h3>
<h4>h4. Bootstrap heading</h4>
<h5>h5. Bootstrap heading</h5>
<h6>h6. Bootstrap heading</h6>

使用通用的<small>标签或.small类在任何标题中创建更轻的次要文本。

h1. Bootstrap heading Secondary text

h2. Bootstrap heading Secondary text

h3. Bootstrap heading Secondary text

h4. Bootstrap heading Secondary text

h5. Bootstrap heading Secondary text

h6. Bootstrap heading Secondary text

<h1>h1. Bootstrap heading <small>Secondary text</small></h1>
<h2>h2. Bootstrap heading <small>Secondary text</small></h2>
<h3>h3. Bootstrap heading <small>Secondary text</small></h3>
<h4>h4. Bootstrap heading <small>Secondary text</small></h4>
<h5>h5. Bootstrap heading <small>Secondary text</small></h5>
<h6>h6. Bootstrap heading <small>Secondary text</small></h6>

正文副本

Bootstrap的全局默认font-size是14px，line-height为1.428。这应用于<body>和所有段落。此外，<p>（段落）接收其计算行高一半的底部边距（默认为10px）。

Nullam quis risus eget urna mollis ornare vel eu leo. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Nullam id dolor id nibh ultricies vehicula.

Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec ullamcorper nulla non metus auctor fringilla. Duis mollis, est non commodo luctus, nisi erat porttitor ligula, eget lacinia odio sem nec elit. Donec ullamcorper nulla non metus auctor fringilla.

Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Duis mollis, est non commodo luctus, nisi erat porttitor ligula, eget lacinia odio sem nec elit.

<p>...</p>

引导正文副本

通过添加.lead使段落突出。

Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor. Duis mollis, est non commodo luctus.

<p class="lead">...</p>

使用Less构建

排版比例基于variables.less中的两个Less变量：@font-size-base和@line-height-base。第一个是全局使用的基础字体大小，第二个是基础行高。我们使用这些变量和一些简单的数学来创建所有类型以及更多的边距、填充和行高。自定义它们，Bootstrap就会适应。

内联文本元素

标记文本

由于文本在另一个上下文中的相关性而突出显示文本，请使用<mark>标签。

You can use the mark tag to highlight text.

You can use the mark tag to <mark>highlight</mark> text.

删除文本

对于指示已被删除的文本块，请使用<del>标签。

~~This line of text is meant to be treated as deleted text.~~

<del>This line of text is meant to be treated as deleted text.</del>

删除线文本

对于指示不再相关的文本块，请使用<s>标签。

~~This line of text is meant to be treated as no longer accurate.~~

<s>This line of text is meant to be treated as no longer accurate.</s>

插入文本

对于指示文档的添加，请使用<ins>标签。

This line of text is meant to be treated as an addition to the document.

<ins>This line of text is meant to be treated as an addition to the document.</ins>

下划线文本

要对文本加下划线，请使用<u>标签。

This line of text will render as underlined

<u>This line of text will render as underlined</u>

使用HTML的默认强调标签和轻量级样式。

小文本

对于淡化内联或文本块，使用<small>标签将文本设置为父级的85%大小。标题元素为嵌套的<small>元素接收自己的font-size。

您也可以使用带有.small的内联元素来替代任何<small>。

This line of text is meant to be treated as fine print.

<small>This line of text is meant to be treated as fine print.</small>

粗体

用于使用更重的字体粗细强调文本片段。

The following snippet of text is rendered as bold text.

<strong>rendered as bold text</strong>

斜体

用于使用斜体强调文本片段。

The following snippet of text is rendered as italicized text.

<em>rendered as italicized text</em>

替代元素

在HTML5中随意使用<b>和<i>。<b>用于突出显示单词或短语而不传达额外的重要性，而<i>主要用于语音、技术术语等。

对齐类

使用文本对齐类轻松重新对齐文本到组件。

Left aligned text.

Center aligned text.

Right aligned text.

Justified text.

No wrap text.

<p class="text-left">Left aligned text.</p>
<p class="text-center">Center aligned text.</p>
<p class="text-right">Right aligned text.</p>
<p class="text-justify">Justified text.</p>
<p class="text-nowrap">No wrap text.</p>

变换类

使用文本大写类在组件中变换文本。

Lowercased text.

Uppercased text.

Capitalized text.

<p class="text-lowercase">Lowercased text.</p>
<p class="text-uppercase">Uppercased text.</p>
<p class="text-capitalize">Capitalized text.</p>

缩写

HTML的<abbr>元素的样式化实现，用于缩写和首字母缩略词，在悬停时显示展开版本。带有title属性的缩写具有浅色点状底部边框和悬停时的帮助光标，为悬停和辅助技术用户提供额外的上下文。

基本缩写

An abbreviation of the word attribute is attr.

<abbr title="attribute">attr</abbr>

首字母缩略词

向缩写添加.initialism以获得稍小的字体大小。

HTML is the best thing since sliced bread.

<abbr title="HyperText Markup Language" class="initialism">HTML</abbr>

地址

显示最近祖先或整个工作主体的联系信息。通过以<br>结束所有行来保持格式。

Twitter, Inc.
795 Folsom Ave, Suite 600
San Francisco, CA 94107
P: (123) 456-7890

Full Name
first.last@example.com

<address>
  <strong>Twitter, Inc.</strong><br>
  795 Folsom Ave, Suite 600<br>
  San Francisco, CA 94107<br>
  <abbr title="Phone">P:</abbr> (123) 456-7890
</address>

<address>
  <strong>Full Name</strong><br>
  <a href="mailto:#">first.last@example.com</a>
</address>

引用块

用于在文档中引用来自另一个来源的内容块。

默认引用块

将<blockquote>包装在任何HTML周围作为引用。对于直接引用，我们推荐<p>。

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.

<blockquote>
  <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.</p>
</blockquote>

引用块选项

标准<blockquote>简单变化的样式和内容更改。

命名来源

添加<footer>来识别来源。将来源作品的名称包装在<cite>中。

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.

Someone famous in Source Title

<blockquote>
  <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.</p>
  <footer>Someone famous in <cite title="Source Title">Source Title</cite></footer>
</blockquote>

替代显示

添加.blockquote-reverse以获得右对齐内容的引用块。

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.

Someone famous in Source Title

<blockquote class="blockquote-reverse">
  ...
</blockquote>

列表

无序

项目顺序不明确重要的项目列表。

Lorem ipsum dolor sit amet
Consectetur adipiscing elit
Integer molestie lorem at massa
Facilisis in pretium nisl aliquet
Nulla volutpat aliquam velit
- Phasellus iaculis neque
- Purus sodales ultricies
- Vestibulum laoreet porttitor sem
- Ac tristique libero volutpat at
Faucibus porta lacus fringilla vel
Aenean sit amet erat nunc
Eget porttitor lorem

<ul>
  <li>...</li>
</ul>

有序

项目顺序确实明确重要的项目列表。

Lorem ipsum dolor sit amet
Consectetur adipiscing elit
Integer molestie lorem at massa
Facilisis in pretium nisl aliquet
Nulla volutpat aliquam velit
Faucibus porta lacus fringilla vel
Aenean sit amet erat nunc
Eget porttitor lorem

<ol>
  <li>...</li>
</ol>

无样式

移除列表项上的默认list-style和左边距（仅限直接子项）。这仅适用于直接子列表项，意味着您还需要为任何嵌套列表添加类。

Lorem ipsum dolor sit amet
Consectetur adipiscing elit
Integer molestie lorem at massa
Facilisis in pretium nisl aliquet
Nulla volutpat aliquam velit
- Phasellus iaculis neque
- Purus sodales ultricies
- Vestibulum laoreet porttitor sem
- Ac tristique libero volutpat at
Faucibus porta lacus fringilla vel
Aenean sit amet erat nunc
Eget porttitor lorem

<ul class="list-unstyled">
  <li>...</li>
</ul>

内联

使用display: inline-block;和一些轻填充将所有列表项放在单行上。

Lorem ipsum
Phasellus iaculis
Nulla volutpat

<ul class="list-inline">
  <li>...</li>
</ul>

描述

术语及其相关描述的列表。

Description lists: A description list is perfect for defining terms.
Euismod: Vestibulum id ligula porta felis euismod semper eget lacinia odio sem nec elit.; Donec id elit non mi porta gravida at eget metus.
Malesuada porta: Etiam porta sem malesuada magna mollis euismod.

<dl>
  <dt>...</dt>
  <dd>...</dd>
</dl>

水平描述

使<dl>中的术语和描述并排排列。开始时像默认的<dl>一样堆叠，但当导航栏展开时，这些也会展开。

Description lists: A description list is perfect for defining terms.
Euismod: Vestibulum id ligula porta felis euismod semper eget lacinia odio sem nec elit.; Donec id elit non mi porta gravida at eget metus.
Malesuada porta: Etiam porta sem malesuada magna mollis euismod.
Felis euismod semper eget lacinia: Fusce dapibus, tellus ac cursus commodo, tortor mauris condimentum nibh, ut fermentum massa justo sit amet risus.

<dl class="dl-horizontal">
  <dt>...</dt>
  <dd>...</dd>
</dl>

自动截断

水平描述列表将截断太长而无法适合左列的术语，使用text-overflow。在较窄的视口中，它们将更改为默认的堆叠布局。

内联

用<code>包装内联代码片段。

For example, <section> should be wrapped as inline.

For example, <code>&lt;section&gt;</code> should be wrapped as inline.

用户输入

使用<kbd>来指示通常通过键盘输入的输入。

To switch directories, type cd followed by the name of the directory.
To edit settings, press ctrl + ,

To switch directories, type <kbd>cd</kbd> followed by the name of the directory.<br>
To edit settings, press <kbd><kbd>ctrl</kbd> + <kbd>,</kbd></kbd>

基本块

使用<pre>处理多行代码。确保转义代码中的任何尖括号以正确渲染。

<p>Sample text here...</p>

<pre>&lt;p&gt;Sample text here...&lt;/p&gt;</pre>

您可以选择添加.pre-scrollable类，这将设置350px的最大高度并提供y轴滚动条。

变量

对于指示变量，请使用<var>标签。

y = mx + b

<var>y</var> = <var>m</var><var>x</var> + <var>b</var>

示例输出

对于指示程序输出块的示例，请使用<samp>标签。

This text is meant to be treated as sample output from a computer program.

<samp>This text is meant to be treated as sample output from a computer program.</samp>

基本示例

对于基本样式—轻填充和仅水平分隔符—向任何<table>添加基类.table。这可能看起来超级冗余，但考虑到表格在其他插件如日历和日期选择器中的广泛使用，我们选择隔离我们的自定义表格样式。

Optional table caption.
#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry	the Bird	@twitter

<table class="table">
  ...
</table>

条纹行

使用.table-striped向<tbody>内的任何表格行添加斑马条纹。

跨浏览器兼容性

条纹表格通过:nth-child CSS选择器进行样式设置，这在Internet Explorer 8中不可用。

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry	the Bird	@twitter

<table class="table table-striped">
  ...
</table>

Bordered table

Add .table-bordered for borders on all sides of the table and cells.

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry	the Bird	@twitter

<table class="table table-bordered">
  ...
</table>

Hover rows

Add .table-hover to enable a hover state on table rows within a <tbody>.

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry	the Bird	@twitter

<table class="table table-hover">
  ...
</table>

Condensed table

Add .table-condensed to make tables more compact by cutting cell padding in half.

#	First Name	Last Name	Username
1	Mark	Otto	@mdo
2	Jacob	Thornton	@fat
3	Larry the Bird		@twitter

<table class="table table-condensed">
  ...
</table>

Contextual classes

Use contextual classes to color table rows or individual cells.

Class	Description
`.active`	Applies the hover color to a particular row or cell
`.success`	Indicates a successful or positive action
`.info`	Indicates a neutral informative change or action
`.warning`	Indicates a warning that might need attention
`.danger`	Indicates a dangerous or potentially negative action

#	Column heading	Column heading	Column heading
1	Column content	Column content	Column content
2	Column content	Column content	Column content
3	Column content	Column content	Column content
4	Column content	Column content	Column content
5	Column content	Column content	Column content
6	Column content	Column content	Column content
7	Column content	Column content	Column content
8	Column content	Column content	Column content
9	Column content	Column content	Column content

<!-- On rows -->
<tr class="active">...</tr>
<tr class="success">...</tr>
<tr class="warning">...</tr>
<tr class="danger">...</tr>
<tr class="info">...</tr>

<!-- On cells (`td` or `th`) -->
<tr>
  <td class="active">...</td>
  <td class="success">...</td>
  <td class="warning">...</td>
  <td class="danger">...</td>
  <td class="info">...</td>
</tr>

Conveying meaning to assistive technologies

Using color to add meaning to a table row or individual cell only provides a visual indication, which will not be conveyed to users of assistive technologies – such as screen readers. Ensure that information denoted by the color is either obvious from the content itself (the visible text in the relevant table row/cell), or is included through alternative means, such as additional text hidden with the .sr-only class.

Responsive tables

Create responsive tables by wrapping any .table in .table-responsive to make them scroll horizontally on small devices (under 768px). When viewing on anything larger than 768px wide, you will not see any difference in these tables.

Vertical clipping/truncation

Responsive tables make use of overflow-y: hidden, which clips off any content that goes beyond the bottom or top edges of the table. In particular, this can clip off dropdown menus and other third-party widgets.

Firefox and fieldsets

Firefox has some awkward fieldset styling involving width that interferes with the responsive table. This cannot be overriden without a Firefox-specific hack that we don't provide in Bootstrap:

@-moz-document url-prefix() {
  fieldset { display: table-cell; }
}

For more information, read this Stack Overflow answer.

#	Table heading	Table heading	Table heading	Table heading	Table heading	Table heading
1	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell
2	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell
3	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell

#	Table heading	Table heading	Table heading	Table heading	Table heading	Table heading
1	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell
2	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell
3	Table cell	Table cell	Table cell	Table cell	Table cell	Table cell

<div class="table-responsive">
  <table class="table">
    ...
  </table>
</div>

Basic example

Individual form controls automatically receive some global styling. All textual <input>, <textarea>, and <select> elements with .form-control are set to width: 100%; by default. Wrap labels and controls in .form-group for optimum spacing.

<form>
  <div class="form-group">
    <label for="exampleInputEmail1">Email address</label>
    <input type="email" class="form-control" id="exampleInputEmail1" placeholder="Email">
  </div>
  <div class="form-group">
    <label for="exampleInputPassword1">Password</label>
    <input type="password" class="form-control" id="exampleInputPassword1" placeholder="Password">
  </div>
  <div class="form-group">
    <label for="exampleInputFile">File input</label>
    <input type="file" id="exampleInputFile">
    <p class="help-block">Example block-level help text here.</p>
  </div>
  <div class="checkbox">
    <label>
      <input type="checkbox"> Check me out
    </label>
  </div>
  <button type="submit" class="btn btn-default">Submit</button>
</form>

Don't mix form groups with input groups

Do not mix form groups directly with input groups. Instead, nest the input group inside of the form group.

Inline form

Add .form-inline to your form (which doesn't have to be a <form>) for left-aligned and inline-block controls. This only applies to forms within viewports that are at least 768px wide.

May require custom widths

Inputs and selects have width: 100%; applied by default in Bootstrap. Within inline forms, we reset that to width: auto; so multiple controls can reside on the same line. Depending on your layout, additional custom widths may be required.

Always add labels

Screen readers will have trouble with your forms if you don't include a label for every input. For these inline forms, you can hide the labels using the .sr-only class. There are further alternative methods of providing a label for assistive technologies, such as the aria-label, aria-labelledby or title attribute. If none of these is present, screen readers may resort to using the placeholder attribute, if present, but note that use of placeholder as a replacement for other labelling methods is not advised.

<form class="form-inline">
  <div class="form-group">
    <label for="exampleInputName2">Name</label>
    <input type="text" class="form-control" id="exampleInputName2" placeholder="Jane Doe">
  </div>
  <div class="form-group">
    <label for="exampleInputEmail2">Email</label>
    <input type="email" class="form-control" id="exampleInputEmail2" placeholder="jane.doe@example.com">
  </div>
  <button type="submit" class="btn btn-default">Send invitation</button>
</form>

<form class="form-inline">
  <div class="form-group">
    <label class="sr-only" for="exampleInputEmail3">Email address</label>
    <input type="email" class="form-control" id="exampleInputEmail3" placeholder="Email">
  </div>
  <div class="form-group">
    <label class="sr-only" for="exampleInputPassword3">Password</label>
    <input type="password" class="form-control" id="exampleInputPassword3" placeholder="Password">
  </div>
  <div class="checkbox">
    <label>
      <input type="checkbox"> Remember me
    </label>
  </div>
  <button type="submit" class="btn btn-default">Sign in</button>
</form>

<form class="form-inline">
  <div class="form-group">
    <label class="sr-only" for="exampleInputAmount">Amount (in dollars)</label>
    <div class="input-group">
      <div class="input-group-addon">$</div>
      <input type="text" class="form-control" id="exampleInputAmount" placeholder="Amount">
      <div class="input-group-addon">.00</div>
    </div>
  </div>
  <button type="submit" class="btn btn-primary">Transfer cash</button>
</form>

Horizontal form

Use Bootstrap's predefined grid classes to align labels and groups of form controls in a horizontal layout by adding .form-horizontal to the form (which doesn't have to be a <form>). Doing so changes .form-groups to behave as grid rows, so no need for .row.

<form class="form-horizontal">
  <div class="form-group">
    <label for="inputEmail3" class="col-sm-2 control-label">Email</label>
    <div class="col-sm-10">
      <input type="email" class="form-control" id="inputEmail3" placeholder="Email">
    </div>
  </div>
  <div class="form-group">
    <label for="inputPassword3" class="col-sm-2 control-label">Password</label>
    <div class="col-sm-10">
      <input type="password" class="form-control" id="inputPassword3" placeholder="Password">
    </div>
  </div>
  <div class="form-group">
    <div class="col-sm-offset-2 col-sm-10">
      <div class="checkbox">
        <label>
          <input type="checkbox"> Remember me
        </label>
      </div>
    </div>
  </div>
  <div class="form-group">
    <div class="col-sm-offset-2 col-sm-10">
      <button type="submit" class="btn btn-default">Sign in</button>
    </div>
  </div>
</form>

Supported controls

Examples of standard form controls supported in an example form layout.

Inputs

Most common form control, text-based input fields. Includes support for all HTML5 types: text, password, datetime, datetime-local, date, month, time, week, number, email, url, search, tel, and color.

Type declaration required

Inputs will only be fully styled if their type is properly declared.

<input type="text" class="form-control" placeholder="Text input">

Input groups

To add integrated text or buttons before and/or after any text-based <input>, check out the input group component.

Textarea

Form control which supports multiple lines of text. Change rows attribute as necessary.

<textarea class="form-control" rows="3"></textarea>

Checkboxes and radios

Checkboxes are for selecting one or several options in a list, while radios are for selecting one option from many.

A checkbox or radio with the disabled attribute will be styled appropriately. To have the <label> for the checkbox or radio also display a "not-allowed" cursor when the user hovers over the label, add the .disabled class to your .radio, .radio-inline, .checkbox, .checkbox-inline, or <fieldset>.

Default (stacked)

<div class="checkbox">
  <label>
    <input type="checkbox" value="">
    Option one is this and that&mdash;be sure to include why it's great
  </label>
</div>
<div class="checkbox disabled">
  <label>
    <input type="checkbox" value="" disabled>
    Option two is disabled
  </label>
</div>

<div class="radio">
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios1" value="option1" checked>
    Option one is this and that&mdash;be sure to include why it's great
  </label>
</div>
<div class="radio">
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios2" value="option2">
    Option two can be something else and selecting it will deselect option one
  </label>
</div>
<div class="radio disabled">
  <label>
    <input type="radio" name="optionsRadios" id="optionsRadios3" value="option3" disabled>
    Option three is disabled
  </label>
</div>

Inline checkboxes and radios

Use the .checkbox-inline or .radio-inline classes on a series of checkboxes or radios for controls that appear on the same line.

<label class="checkbox-inline">
  <input type="checkbox" id="inlineCheckbox1" value="option1"> 1
</label>
<label class="checkbox-inline">
  <input type="checkbox" id="inlineCheckbox2" value="option2"> 2
</label>
<label class="checkbox-inline">
  <input type="checkbox" id="inlineCheckbox3" value="option3"> 3
</label>

<label class="radio-inline">
  <input type="radio" name="inlineRadioOptions" id="inlineRadio1" value="option1"> 1
</label>
<label class="radio-inline">
  <input type="radio" name="inlineRadioOptions" id="inlineRadio2" value="option2"> 2
</label>
<label class="radio-inline">
  <input type="radio" name="inlineRadioOptions" id="inlineRadio3" value="option3"> 3
</label>

Checkboxes and radios without label text

Should you have no text within the <label>, the input is positioned as you'd expect. Currently only works on non-inline checkboxes and radios. Remember to still provide some form of label for assistive technologies (for instance, using aria-label).

<div class="checkbox">
  <label>
    <input type="checkbox" id="blankCheckbox" value="option1" aria-label="...">
  </label>
</div>
<div class="radio">
  <label>
    <input type="radio" name="blankRadio" id="blankRadio1" value="option1" aria-label="...">
  </label>
</div>

Selects

Note that many native select menus—namely in Safari and Chrome—have rounded corners that cannot be modified via border-radius properties.

<select class="form-control">
  <option>1</option>
  <option>2</option>
  <option>3</option>
  <option>4</option>
  <option>5</option>
</select>

For <select> controls with the multiple attribute, multiple options are shown by default.

<select multiple class="form-control">
  <option>1</option>
  <option>2</option>
  <option>3</option>
  <option>4</option>
  <option>5</option>
</select>

Static control

When you need to place plain text next to a form label within a form, use the .form-control-static class on a <p>.

<form class="form-horizontal">
  <div class="form-group">
    <label class="col-sm-2 control-label">Email</label>
    <div class="col-sm-10">
      <p class="form-control-static">email@example.com</p>
    </div>
  </div>
  <div class="form-group">
    <label for="inputPassword" class="col-sm-2 control-label">Password</label>
    <div class="col-sm-10">
      <input type="password" class="form-control" id="inputPassword" placeholder="Password">
    </div>
  </div>
</form>

<form class="form-inline">
  <div class="form-group">
    <label class="sr-only">Email</label>
    <p class="form-control-static">email@example.com</p>
  </div>
  <div class="form-group">
    <label for="inputPassword2" class="sr-only">Password</label>
    <input type="password" class="form-control" id="inputPassword2" placeholder="Password">
  </div>
  <button type="submit" class="btn btn-default">Confirm identity</button>
</form>

Focus state

We remove the default outline styles on some form controls and apply a box-shadow in its place for :focus.

Demo `:focus` state

The above example input uses custom styles in our documentation to demonstrate the :focus state on a .form-control.

Disabled state

Add the disabled boolean attribute on an input to prevent user interactions. Disabled inputs appear lighter and add a not-allowed cursor.

<input class="form-control" id="disabledInput" type="text" placeholder="Disabled input here..." disabled>

Disabled fieldsets

Add the disabled attribute to a <fieldset> to disable all the controls within the <fieldset> at once.

Caveat about link functionality of `<a>`

By default, browsers will treat all native form controls (<input>, <select> and <button> elements) inside a <fieldset disabled> as disabled, preventing both keyboard and mouse interactions on them. However, if your form also includes <a ... class="btn btn-*"> elements, these will only be given a style of pointer-events: none. As noted in the section about disabled state for buttons (and specifically in the sub-section for anchor elements), this CSS property is not yet standardized and isn't fully supported in Opera 18 and below, or in Internet Explorer 11, and won't prevent keyboard users from being able to focus or activate these links. So to be safe, use custom JavaScript to disable such links.

Cross-browser compatibility

While Bootstrap will apply these styles in all browsers, Internet Explorer 11 and below don't fully support the disabled attribute on a <fieldset>. Use custom JavaScript to disable the fieldset in these browsers.

<form>
  <fieldset disabled>
    <div class="form-group">
      <label for="disabledTextInput">Disabled input</label>
      <input type="text" id="disabledTextInput" class="form-control" placeholder="Disabled input">
    </div>
    <div class="form-group">
      <label for="disabledSelect">Disabled select menu</label>
      <select id="disabledSelect" class="form-control">
        <option>Disabled select</option>
      </select>
    </div>
    <div class="checkbox">
      <label>
        <input type="checkbox"> Can't check this
      </label>
    </div>
    <button type="submit" class="btn btn-primary">Submit</button>
  </fieldset>
</form>

Readonly state

Add the readonly boolean attribute on an input to prevent modification of the input's value. Read-only inputs appear lighter (just like disabled inputs), but retain the standard cursor.

<input class="form-control" type="text" placeholder="Readonly input here…" readonly>

Validation states

Bootstrap includes validation styles for error, warning, and success states on form controls. To use, add .has-warning, .has-error, or .has-success to the parent element. Any .control-label, .form-control, and .help-block within that element will receive the validation styles.

Conveying validation state to assistive technologies and colorblind users

Using these validation styles to denote the state of a form control only provides a visual, color-based indication, which will not be conveyed to users of assistive technologies - such as screen readers - or to colorblind users.

Ensure that an alternative indication of state is also provided. For instance, you can include a hint about state in the form control's <label> text itself (as is the case in the following code example), include a Glyphicon (with appropriate alternative text using the .sr-only class - see the Glyphicon examples), or by providing an additional help text block. Specifically for assistive technologies, invalid form controls can also be assigned an aria-invalid="true" attribute.

<div class="form-group has-success">
  <label class="control-label" for="inputSuccess1">Input with success</label>
  <input type="text" class="form-control" id="inputSuccess1">
</div>
<div class="form-group has-warning">
  <label class="control-label" for="inputWarning1">Input with warning</label>
  <input type="text" class="form-control" id="inputWarning1">
</div>
<div class="form-group has-error">
  <label class="control-label" for="inputError1">Input with error</label>
  <input type="text" class="form-control" id="inputError1">
</div>
<div class="has-success">
  <div class="checkbox">
    <label>
      <input type="checkbox" id="checkboxSuccess" value="option1">
      Checkbox with success
    </label>
  </div>
</div>
<div class="has-warning">
  <div class="checkbox">
    <label>
      <input type="checkbox" id="checkboxWarning" value="option1">
      Checkbox with warning
    </label>
  </div>
</div>
<div class="has-error">
  <div class="checkbox">
    <label>
      <input type="checkbox" id="checkboxError" value="option1">
      Checkbox with error
    </label>
  </div>
</div>

With optional icons

You can also add optional feedback icons with the addition of .has-feedback and the right icon.

Feedback icons only work with textual <input class="form-control"> elements.

Icons, labels, and input groups

Manual positioning of feedback icons is required for inputs without a label and for input groups with an add-on on the right. You are strongly encouraged to provide labels for all inputs for accessibility reasons. If you wish to prevent labels from being displayed, hide them with the .sr-only class. If you must do without labels, adjust the top value of the feedback icon. For input groups, adjust the right value to an appropriate pixel value depending on the width of your addon.

Conveying the icon's meaning to assistive technologies

To ensure that assistive technologies – such as screen readers – correctly convey the meaning of an icon, additional hidden text should be included with the .sr-only class and explicitly associated with the form control it relates to using aria-describedby. Alternatively, ensure that the meaning (for instance, the fact that there is a warning for a particular text entry field) is conveyed in some other form, such as changing the text of the actual <label> associated with the form control.

Although the following examples already mention the validation state of their respective form controls in the <label> text itself, the above technique (using .sr-only text and aria-describedby) has been included for illustrative purposes.

<div class="form-group has-success has-feedback">
  <label class="control-label" for="inputSuccess2">Input with success</label>
  <input type="text" class="form-control" id="inputSuccess2" aria-describedby="inputSuccess2Status">
  <span class="glyphicon glyphicon-ok form-control-feedback" aria-hidden="true"></span>
  <span id="inputSuccess2Status" class="sr-only">(success)</span>
</div>
<div class="form-group has-warning has-feedback">
  <label class="control-label" for="inputWarning2">Input with warning</label>
  <input type="text" class="form-control" id="inputWarning2" aria-describedby="inputWarning2Status">
  <span class="glyphicon glyphicon-warning-sign form-control-feedback" aria-hidden="true"></span>
  <span id="inputWarning2Status" class="sr-only">(warning)</span>
</div>
<div class="form-group has-error has-feedback">
  <label class="control-label" for="inputError2">Input with error</label>
  <input type="text" class="form-control" id="inputError2" aria-describedby="inputError2Status">
  <span class="glyphicon glyphicon-remove form-control-feedback" aria-hidden="true"></span>
  <span id="inputError2Status" class="sr-only">(error)</span>
</div>
<div class="form-group has-success has-feedback">
  <label class="control-label" for="inputGroupSuccess1">Input group with success</label>
  <div class="input-group">
    <span class="input-group-addon">@</span>
    <input type="text" class="form-control" id="inputGroupSuccess1" aria-describedby="inputGroupSuccess1Status">
  </div>
  <span class="glyphicon glyphicon-ok form-control-feedback" aria-hidden="true"></span>
  <span id="inputGroupSuccess1Status" class="sr-only">(success)</span>
</div>

Optional icons in horizontal and inline forms

<form class="form-horizontal">
  <div class="form-group has-success has-feedback">
    <label class="control-label col-sm-3" for="inputSuccess3">Input with success</label>
    <div class="col-sm-9">
      <input type="text" class="form-control" id="inputSuccess3" aria-describedby="inputSuccess3Status">
      <span class="glyphicon glyphicon-ok form-control-feedback" aria-hidden="true"></span>
      <span id="inputSuccess3Status" class="sr-only">(success)</span>
    </div>
  </div>
  <div class="form-group has-success has-feedback">
    <label class="control-label col-sm-3" for="inputGroupSuccess2">Input group with success</label>
    <div class="col-sm-9">
      <div class="input-group">
        <span class="input-group-addon">@</span>
        <input type="text" class="form-control" id="inputGroupSuccess2" aria-describedby="inputGroupSuccess2Status">
      </div>
      <span class="glyphicon glyphicon-ok form-control-feedback" aria-hidden="true"></span>
      <span id="inputGroupSuccess2Status" class="sr-only">(success)</span>
    </div>
  </div>
</form>

<form class="form-inline">
  <div class="form-group has-success has-feedback">
    <label class="control-label" for="inputSuccess4">Input with success</label>
    <input type="text" class="form-control" id="inputSuccess4" aria-describedby="inputSuccess4Status">
    <span class="glyphicon glyphicon-ok form-control-feedback" aria-hidden="true"></span>
    <span id="inputSuccess4Status" class="sr-only">(success)</span>
  </div>
</form>
<form class="form-inline">
  <div class="form-group has-success has-feedback">
    <label class="control-label" for="inputGroupSuccess3">Input group with success</label>
    <div class="input-group">
      <span class="input-group-addon">@</span>
      <input type="text" class="form-control" id="inputGroupSuccess3" aria-describedby="inputGroupSuccess3Status">
    </div>
    <span class="glyphicon glyphicon-ok form-control-feedback" aria-hidden="true"></span>
    <span id="inputGroupSuccess3Status" class="sr-only">(success)</span>
  </div>
</form>

Optional icons with hidden `.sr-only` labels

If you use the .sr-only class to hide a form control's <label> (rather than using other labelling options, such as the aria-label attribute), Bootstrap will automatically adjust the position of the icon once it's been added.

<div class="form-group has-success has-feedback">
  <label class="control-label sr-only" for="inputSuccess5">Hidden label</label>
  <input type="text" class="form-control" id="inputSuccess5" aria-describedby="inputSuccess5Status">
  <span class="glyphicon glyphicon-ok form-control-feedback" aria-hidden="true"></span>
  <span id="inputSuccess5Status" class="sr-only">(success)</span>
</div>
<div class="form-group has-success has-feedback">
  <label class="control-label sr-only" for="inputGroupSuccess4">Input group with success</label>
  <div class="input-group">
    <span class="input-group-addon">@</span>
    <input type="text" class="form-control" id="inputGroupSuccess4" aria-describedby="inputGroupSuccess4Status">
  </div>
  <span class="glyphicon glyphicon-ok form-control-feedback" aria-hidden="true"></span>
  <span id="inputGroupSuccess4Status" class="sr-only">(success)</span>
</div>

Control sizing

Set heights using classes like .input-lg, and set widths using grid column classes like .col-lg-*.

Height sizing

Create taller or shorter form controls that match button sizes.

<input class="form-control input-lg" type="text" placeholder=".input-lg">
<input class="form-control" type="text" placeholder="Default input">
<input class="form-control input-sm" type="text" placeholder=".input-sm">

<select class="form-control input-lg">...</select>
<select class="form-control">...</select>
<select class="form-control input-sm">...</select>

Horizontal form group sizes

Quickly size labels and form controls within .form-horizontal by adding .form-group-lg or .form-group-sm.

<form class="form-horizontal">
  <div class="form-group form-group-lg">
    <label class="col-sm-2 control-label" for="formGroupInputLarge">Large label</label>
    <div class="col-sm-10">
      <input class="form-control" type="text" id="formGroupInputLarge" placeholder="Large input">
    </div>
  </div>
  <div class="form-group form-group-sm">
    <label class="col-sm-2 control-label" for="formGroupInputSmall">Small label</label>
    <div class="col-sm-10">
      <input class="form-control" type="text" id="formGroupInputSmall" placeholder="Small input">
    </div>
  </div>
</form>

Column sizing

Wrap inputs in grid columns, or any custom parent element, to easily enforce desired widths.

<div class="row">
  <div class="col-xs-2">
    <input type="text" class="form-control" placeholder=".col-xs-2">
  </div>
  <div class="col-xs-3">
    <input type="text" class="form-control" placeholder=".col-xs-3">
  </div>
  <div class="col-xs-4">
    <input type="text" class="form-control" placeholder=".col-xs-4">
  </div>
</div>

Help text

Block level help text for form controls.

Associating help text with form controls

Help text should be explicitly associated with the form control it relates to using the aria-describedby attribute. This will ensure that assistive technologies – such as screen readers – will announce this help text when the user focuses or enters the control.

<label class="sr-only" for="inputHelpBlock">Input with help text</label>
<input type="text" id="inputHelpBlock" class="form-control" aria-describedby="helpBlock">
...
<span id="helpBlock" class="help-block">A block of help text that breaks onto a new line and may extend beyond one line.</span>

Button tags

Use the button classes on an <a>, <button>, or <input> element.

<a class="btn btn-default" href="#" role="button">Link</a>
<button class="btn btn-default" type="submit">Button</button>
<input class="btn btn-default" type="button" value="Input">
<input class="btn btn-default" type="submit" value="Submit">

Context-specific usage

While button classes can be used on <a> and <button> elements, only <button> elements are supported within our nav and navbar components.

Links acting as buttons

If the <a> elements are used to act as buttons – triggering in-page functionality, rather than navigating to another document or section within the current page – they should also be given an appropriate role="button".

Cross-browser rendering

As a best practice, we highly recommend using the <button> element whenever possible to ensure matching cross-browser rendering.

Among other things, there's a bug in Firefox <30 that prevents us from setting the line-height of <input>-based buttons, causing them to not exactly match the height of other buttons on Firefox.

Options

Use any of the available button classes to quickly create a styled button.

<!-- Standard button -->
<button type="button" class="btn btn-default">Default</button>

<!-- Provides extra visual weight and identifies the primary action in a set of buttons -->
<button type="button" class="btn btn-primary">Primary</button>

<!-- Indicates a successful or positive action -->
<button type="button" class="btn btn-success">Success</button>

<!-- Contextual button for informational alert messages -->
<button type="button" class="btn btn-info">Info</button>

<!-- Indicates caution should be taken with this action -->
<button type="button" class="btn btn-warning">Warning</button>

<!-- Indicates a dangerous or potentially negative action -->
<button type="button" class="btn btn-danger">Danger</button>

<!-- Deemphasize a button by making it look like a link while maintaining button behavior -->
<button type="button" class="btn btn-link">Link</button>

Conveying meaning to assistive technologies

Using color to add meaning to a button only provides a visual indication, which will not be conveyed to users of assistive technologies – such as screen readers. Ensure that information denoted by the color is either obvious from the content itself (the visible text of the button), or is included through alternative means, such as additional text hidden with the .sr-only class.

Sizes

Fancy larger or smaller buttons? Add .btn-lg, .btn-sm, or .btn-xs for additional sizes.

<p>
  <button type="button" class="btn btn-primary btn-lg">Large button</button>
  <button type="button" class="btn btn-default btn-lg">Large button</button>
</p>
<p>
  <button type="button" class="btn btn-primary">Default button</button>
  <button type="button" class="btn btn-default">Default button</button>
</p>
<p>
  <button type="button" class="btn btn-primary btn-sm">Small button</button>
  <button type="button" class="btn btn-default btn-sm">Small button</button>
</p>
<p>
  <button type="button" class="btn btn-primary btn-xs">Extra small button</button>
  <button type="button" class="btn btn-default btn-xs">Extra small button</button>
</p>

Create block level buttons—those that span the full width of a parent— by adding .btn-block.

<button type="button" class="btn btn-primary btn-lg btn-block">Block level button</button>
<button type="button" class="btn btn-default btn-lg btn-block">Block level button</button>

Active state

Buttons will appear pressed (with a darker background, darker border, and inset shadow) when active. For <button> elements, this is done via :active. For <a> elements, it's done with .active. However, you may use .active on <button>s (and include the aria-pressed="true" attribute) should you need to replicate the active state programmatically.

Button element

No need to add :active as it's a pseudo-class, but if you need to force the same appearance, go ahead and add .active.

<button type="button" class="btn btn-primary btn-lg active">Primary button</button>
<button type="button" class="btn btn-default btn-lg active">Button</button>

Anchor element

Add the .active class to <a> buttons.

Primary link Link

<a href="#" class="btn btn-primary btn-lg active" role="button">Primary link</a>
<a href="#" class="btn btn-default btn-lg active" role="button">Link</a>

Disabled state

Make buttons look unclickable by fading them back with opacity.

Button element

Add the disabled attribute to <button> buttons.

<button type="button" class="btn btn-lg btn-primary" disabled="disabled">Primary button</button>
<button type="button" class="btn btn-default btn-lg" disabled="disabled">Button</button>

Cross-browser compatibility

If you add the disabled attribute to a <button>, Internet Explorer 9 and below will render text gray with a nasty text-shadow that we cannot fix.

Anchor element

Add the .disabled class to <a> buttons.

Primary link Link

<a href="#" class="btn btn-primary btn-lg disabled" role="button">Primary link</a>
<a href="#" class="btn btn-default btn-lg disabled" role="button">Link</a>

We use .disabled as a utility class here, similar to the common .active class, so no prefix is required.

Link functionality caveat

This class uses pointer-events: none to try to disable the link functionality of <a>s, but that CSS property is not yet standardized and isn't fully supported in Opera 18 and below, or in Internet Explorer 11. In addition, even in browsers that do support pointer-events: none, keyboard navigation remains unaffected, meaning that sighted keyboard users and users of assistive technologies will still be able to activate these links. So to be safe, use custom JavaScript to disable such links.

Responsive images

Images in Bootstrap 3 can be made responsive-friendly via the addition of the .img-responsive class. This applies max-width: 100%;, height: auto; and display: block; to the image so that it scales nicely to the parent element.

To center images which use the .img-responsive class, use .center-block instead of .text-center. See the helper classes section for more details about .center-block usage.

SVG images and IE 8-10

In Internet Explorer 8-10, SVG images with .img-responsive are disproportionately sized. To fix this, add width: 100% \9; where necessary. Bootstrap doesn't apply this automatically as it causes complications to other image formats.

<img src="..." class="img-responsive" alt="Responsive image">

Image shapes

Add classes to an <img> element to easily style images in any project.

Cross-browser compatibility

Keep in mind that Internet Explorer 8 lacks support for rounded corners.

A generic square placeholder image with rounded corners

A generic square placeholder image where only the portion within the circle circumscribed about said square is visible

A generic square placeholder image with a white border around it, making it resemble a photograph taken with an old instant camera

<img src="..." alt="..." class="img-rounded">
<img src="..." alt="..." class="img-circle">
<img src="..." alt="..." class="img-thumbnail">

Contextual colors

Convey meaning through color with a handful of emphasis utility classes. These may also be applied to links and will darken on hover just like our default link styles.

Fusce dapibus, tellus ac cursus commodo, tortor mauris nibh.

Nullam id dolor id nibh ultricies vehicula ut id elit.

Duis mollis, est non commodo luctus, nisi erat porttitor ligula.

Maecenas sed diam eget risus varius blandit sit amet non magna.

Etiam porta sem malesuada magna mollis euismod.

Donec ullamcorper nulla non metus auctor fringilla.

<p class="text-muted">...</p>
<p class="text-primary">...</p>
<p class="text-success">...</p>
<p class="text-info">...</p>
<p class="text-warning">...</p>
<p class="text-danger">...</p>

Dealing with specificity

Sometimes emphasis classes cannot be applied due to the specificity of another selector. In most cases, a sufficient workaround is to wrap your text in a <span> with the class.

Conveying meaning to assistive technologies

Using color to add meaning only provides a visual indication, which will not be conveyed to users of assistive technologies – such as screen readers. Ensure that information denoted by the color is either obvious from the content itself (the contextual colors are only used to reinforce meaning that is already present in the text/markup), or is included through alternative means, such as additional text hidden with the .sr-only class.

Contextual backgrounds

Similar to the contextual text color classes, easily set the background of an element to any contextual class. Anchor components will darken on hover, just like the text classes.

Nullam id dolor id nibh ultricies vehicula ut id elit.

Duis mollis, est non commodo luctus, nisi erat porttitor ligula.

Maecenas sed diam eget risus varius blandit sit amet non magna.

Etiam porta sem malesuada magna mollis euismod.

Donec ullamcorper nulla non metus auctor fringilla.

<p class="bg-primary">...</p>
<p class="bg-success">...</p>
<p class="bg-info">...</p>
<p class="bg-warning">...</p>
<p class="bg-danger">...</p>

Dealing with specificity

Sometimes contextual background classes cannot be applied due to the specificity of another selector. In some cases, a sufficient workaround is to wrap your element's content in a <div> with the class.

Conveying meaning to assistive technologies

As with contextual colors, ensure that any meaning conveyed through color is also conveyed in a format that is not purely presentational.

Close icon

Use the generic close icon for dismissing content like modals and alerts.

<button type="button" class="close" aria-label="Close"><span aria-hidden="true">&times;</span></button>

Carets

Use carets to indicate dropdown functionality and direction. Note that the default caret will reverse automatically in dropup menus.

<span class="caret"></span>

Quick floats

Float an element to the left or right with a class. !important is included to avoid specificity issues. Classes can also be used as mixins.

<div class="pull-left">...</div>
<div class="pull-right">...</div>

// Classes
.pull-left {
  float: left !important;
}
.pull-right {
  float: right !important;
}

// Usage as mixins
.element {
  .pull-left();
}
.another-element {
  .pull-right();
}

Center content blocks

Set an element to display: block and center via margin. Available as a mixin and class.

<div class="center-block">...</div>

// Class
.center-block {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

// Usage as a mixin
.element {
  .center-block();
}

Clearfix

Easily clear floats by adding .clearfix to the parent element. Utilizes the micro clearfix as popularized by Nicolas Gallagher. Can also be used as a mixin.

<!-- Usage as a class -->
<div class="clearfix">...</div>

// Mixin itself
.clearfix() {
  &:before,
  &:after {
    content: " ";
    display: table;
  }
  &:after {
    clear: both;
  }
}

// Usage as a mixin
.element {
  .clearfix();
}

Showing and hiding content

Force an element to be shown or hidden (including for screen readers) with the use of .show and .hidden classes. These classes use !important to avoid specificity conflicts, just like the quick floats. They are only available for block level toggling. They can also be used as mixins.

.hide is available, but it does not always affect screen readers and is deprecated as of v3.0.1. Use .hidden or .sr-only instead.

Furthermore, .invisible can be used to toggle only the visibility of an element, meaning its display is not modified and the element can still affect the flow of the document.

<div class="show">...</div>
<div class="hidden">...</div>

// Classes
.show {
  display: block !important;
}
.hidden {
  display: none !important;
}
.invisible {
  visibility: hidden;
}

// Usage as mixins
.element {
  .show();
}
.another-element {
  .hidden();
}

Screen reader and keyboard navigation content

Hide an element to all devices except screen readers with .sr-only. Combine .sr-only with .sr-only-focusable to show the element again when it's focused (e.g. by a keyboard-only user). Necessary for following accessibility best practices. Can also be used as mixins.

<a class="sr-only sr-only-focusable" href="#content">Skip to main content</a>

// Usage as a mixin
.skip-navigation {
  .sr-only();
  .sr-only-focusable();
}

Image replacement

Utilize the .text-hide class or mixin to help replace an element's text content with a background image.

<h1 class="text-hide">Custom heading</h1>

// Usage as a mixin
.heading {
  .text-hide();
}

For faster mobile-friendly development, use these utility classes for showing and hiding content by device via media query. Also included are utility classes for toggling content when printed.

Try to use these on a limited basis and avoid creating entirely different versions of the same site. Instead, use them to complement each device's presentation.

Available classes

Use a single or combination of the available classes for toggling content across viewport breakpoints.

	Extra small devices Phones (<768px)	Small devices Tablets (≥768px)	Medium devices Desktops (≥992px)	Large devices Desktops (≥1200px)
`.visible-xs-*`	Visible	Hidden	Hidden	Hidden
`.visible-sm-*`	Hidden	Visible	Hidden	Hidden
`.visible-md-*`	Hidden	Hidden	Visible	Hidden
`.visible-lg-*`	Hidden	Hidden	Hidden	Visible
`.hidden-xs`	Hidden	Visible	Visible	Visible
`.hidden-sm`	Visible	Hidden	Visible	Visible
`.hidden-md`	Visible	Visible	Hidden	Visible
`.hidden-lg`	Visible	Visible	Visible	Hidden

As of v3.2.0, the .visible-*-* classes for each breakpoint come in three variations, one for each CSS display property value listed below.

Group of classes	CSS `display`
`.visible-*-block`	`display: block;`
`.visible-*-inline`	`display: inline;`
`.visible-*-inline-block`	`display: inline-block;`

So, for extra small (xs) screens for example, the available .visible-*-* classes are: .visible-xs-block, .visible-xs-inline, and .visible-xs-inline-block.

The classes .visible-xs, .visible-sm, .visible-md, and .visible-lg also exist, but are deprecated as of v3.2.0. They are approximately equivalent to .visible-*-block, except with additional special cases for toggling <table>-related elements.

Print classes

Similar to the regular responsive classes, use these for toggling content for print.

Classes	Browser	Print
`.visible-print-block` `.visible-print-inline` `.visible-print-inline-block`	Hidden	Visible
`.hidden-print`	Visible	Hidden

The class .visible-print also exists but is deprecated as of v3.2.0. It is approximately equivalent to .visible-print-block, except with additional special cases for <table>-related elements.

Test cases

Resize your browser or load on different devices to test the responsive utility classes.

Visible on...

Green checkmarks indicate the element is visible in your current viewport.

Extra small ✔ Visible on x-small

Small ✔ Visible on small

Medium ✔ Visible on medium

Large ✔ Visible on large

Extra small and small ✔ Visible on x-small and small

Medium and large ✔ Visible on medium and large

Extra small and medium ✔ Visible on x-small and medium

Small and large ✔ Visible on small and large

Extra small and large ✔ Visible on x-small and large

Small and medium ✔ Visible on small and medium

Hidden on...

Here, green checkmarks also indicate the element is hidden in your current viewport.

Extra small ✔ Hidden on x-small

Small ✔ Hidden on small

Medium ✔ Hidden on medium

Large ✔ Hidden on large

Extra small and small ✔ Hidden on x-small and small

Medium and large ✔ Hidden on medium and large

Extra small and medium ✔ Hidden on x-small and medium

Small and large ✔ Hidden on small and large

Extra small and large ✔ Hidden on x-small and large

Small and medium ✔ Hidden on small and medium

Bootstrap's CSS is built on Less, a preprocessor with additional functionality like variables, mixins, and functions for compiling CSS. Those looking to use the source Less files instead of our compiled CSS files can make use of the numerous variables and mixins we use throughout the framework.

Grid variables and mixins are covered within the Grid system section.

Compiling Bootstrap

Bootstrap can be used in at least two ways: with the compiled CSS or with the source Less files. To compile the Less files, consult the Getting Started section for how to setup your development environment to run the necessary commands.

Third party compilation tools may work with Bootstrap, but they are not supported by our core team.

Variables

Variables are used throughout the entire project as a way to centralize and share commonly used values like colors, spacing, or font stacks. For a complete breakdown, please see the Customizer.

Colors

Easily make use of two color schemes: grayscale and semantic. Grayscale colors provide quick access to commonly used shades of black while semantic include various colors assigned to meaningful contextual values.

@gray-darker:  lighten(#000, 13.5%); // #222
@gray-dark:    lighten(#000, 20%);   // #333
@gray:         lighten(#000, 33.5%); // #555
@gray-light:   lighten(#000, 46.7%); // #777
@gray-lighter: lighten(#000, 93.5%); // #eee

@brand-primary: darken(#428bca, 6.5%); // #337ab7
@brand-success: #5cb85c;
@brand-info:    #5bc0de;
@brand-warning: #f0ad4e;
@brand-danger:  #d9534f;

Use any of these color variables as they are or reassign them to more meaningful variables for your project.

// Use as-is
.masthead {
  background-color: @brand-primary;
}

// Reassigned variables in Less
@alert-message-background: @brand-info;
.alert {
  background-color: @alert-message-background;
}

Scaffolding

A handful of variables for quickly customizing key elements of your site's skeleton.

// Scaffolding
@body-bg:    #fff;
@text-color: @black-50;

Links

Easily style your links with the right color with only one value.

// Variables
@link-color:       @brand-primary;
@link-hover-color: darken(@link-color, 15%);

// Usage
a {
  color: @link-color;
  text-decoration: none;

  &:hover {
    color: @link-hover-color;
    text-decoration: underline;
  }
}

Note that the @link-hover-color uses a function, another awesome tool from Less, to automagically create the right hover color. You can use darken, lighten, saturate, and desaturate.

Typography

Easily set your typeface, text size, leading, and more with a few quick variables. Bootstrap makes use of these as well to provide easy typographic mixins.

@font-family-sans-serif:  "Helvetica Neue", Helvetica, Arial, sans-serif;
@font-family-serif:       Georgia, "Times New Roman", Times, serif;
@font-family-monospace:   Menlo, Monaco, Consolas, "Courier New", monospace;
@font-family-base:        @font-family-sans-serif;

@font-size-base:          14px;
@font-size-large:         ceil((@font-size-base * 1.25)); // ~18px
@font-size-small:         ceil((@font-size-base * 0.85)); // ~12px

@font-size-h1:            floor((@font-size-base * 2.6)); // ~36px
@font-size-h2:            floor((@font-size-base * 2.15)); // ~30px
@font-size-h3:            ceil((@font-size-base * 1.7)); // ~24px
@font-size-h4:            ceil((@font-size-base * 1.25)); // ~18px
@font-size-h5:            @font-size-base;
@font-size-h6:            ceil((@font-size-base * 0.85)); // ~12px

@line-height-base:        1.428571429; // 20/14
@line-height-computed:    floor((@font-size-base * @line-height-base)); // ~20px

@headings-font-family:    inherit;
@headings-font-weight:    500;
@headings-line-height:    1.1;
@headings-color:          inherit;

Icons

Two quick variables for customizing the location and filename of your icons.

@icon-font-path:          "../fonts/";
@icon-font-name:          "glyphicons-halflings-regular";

Components

Components throughout Bootstrap make use of some default variables for setting common values. Here are the most commonly used.

@padding-base-vertical:          6px;
@padding-base-horizontal:        12px;

@padding-large-vertical:         10px;
@padding-large-horizontal:       16px;

@padding-small-vertical:         5px;
@padding-small-horizontal:       10px;

@padding-xs-vertical:            1px;
@padding-xs-horizontal:          5px;

@line-height-large:              1.33;
@line-height-small:              1.5;

@border-radius-base:             4px;
@border-radius-large:            6px;
@border-radius-small:            3px;

@component-active-color:         #fff;
@component-active-bg:            @brand-primary;

@caret-width-base:               4px;
@caret-width-large:              5px;

Vendor mixins

Vendor mixins are mixins to help support multiple browsers by including all relevant vendor prefixes in your compiled CSS.

Box-sizing

Reset your components' box model with a single mixin. For context, see this helpful article from Mozilla.

The mixin is deprecated as of v3.2.0, with the introduction of Autoprefixer. To preserve backwards-compatibility, Bootstrap will continue to use the mixin internally until Bootstrap v4.

.box-sizing(@box-model) {
  -webkit-box-sizing: @box-model; // Safari <= 5
     -moz-box-sizing: @box-model; // Firefox <= 19
          box-sizing: @box-model;
}

Rounded corners

Today all modern browsers support the non-prefixed border-radius property. As such, there is no .border-radius() mixin, but Bootstrap does include shortcuts for quickly rounding two corners on a particular side of an object.

.border-top-radius(@radius) {
  border-top-right-radius: @radius;
   border-top-left-radius: @radius;
}
.border-right-radius(@radius) {
  border-bottom-right-radius: @radius;
     border-top-right-radius: @radius;
}
.border-bottom-radius(@radius) {
  border-bottom-right-radius: @radius;
   border-bottom-left-radius: @radius;
}
.border-left-radius(@radius) {
  border-bottom-left-radius: @radius;
     border-top-left-radius: @radius;
}

Box (Drop) shadows

If your target audience is using the latest and greatest browsers and devices, be sure to just use the box-shadow property on its own. If you need support for older Android (pre-v4) and iOS devices (pre-iOS 5), use the deprecated mixin to pick up the required -webkit prefix.

The mixin is deprecated as of v3.1.0, since Bootstrap doesn't officially support the outdated platforms that don't support the standard property. To preserve backwards-compatibility, Bootstrap will continue to use the mixin internally until Bootstrap v4.

Be sure to use rgba() colors in your box shadows so they blend as seamlessly as possible with backgrounds.

.box-shadow(@shadow: 0 1px 3px rgba(0,0,0,.25)) {
  -webkit-box-shadow: @shadow; // iOS <4.3 & Android <4.1
          box-shadow: @shadow;
}

Transitions

Multiple mixins for flexibility. Set all transition information with one, or specify a separate delay and duration as needed.

The mixins are deprecated as of v3.2.0, with the introduction of Autoprefixer. To preserve backwards-compatibility, Bootstrap will continue to use the mixins internally until Bootstrap v4.

.transition(@transition) {
  -webkit-transition: @transition;
          transition: @transition;
}
.transition-property(@transition-property) {
  -webkit-transition-property: @transition-property;
          transition-property: @transition-property;
}
.transition-delay(@transition-delay) {
  -webkit-transition-delay: @transition-delay;
          transition-delay: @transition-delay;
}
.transition-duration(@transition-duration) {
  -webkit-transition-duration: @transition-duration;
          transition-duration: @transition-duration;
}
.transition-timing-function(@timing-function) {
  -webkit-transition-timing-function: @timing-function;
          transition-timing-function: @timing-function;
}
.transition-transform(@transition) {
  -webkit-transition: -webkit-transform @transition;
     -moz-transition: -moz-transform @transition;
       -o-transition: -o-transform @transition;
          transition: transform @transition;
}

Transformations

Rotate, scale, translate (move), or skew any object.

The mixins are deprecated as of v3.2.0, with the introduction of Autoprefixer. To preserve backwards-compatibility, Bootstrap will continue to use the mixins internally until Bootstrap v4.

.rotate(@degrees) {
  -webkit-transform: rotate(@degrees);
      -ms-transform: rotate(@degrees); // IE9 only
          transform: rotate(@degrees);
}
.scale(@ratio; @ratio-y...) {
  -webkit-transform: scale(@ratio, @ratio-y);
      -ms-transform: scale(@ratio, @ratio-y); // IE9 only
          transform: scale(@ratio, @ratio-y);
}
.translate(@x; @y) {
  -webkit-transform: translate(@x, @y);
      -ms-transform: translate(@x, @y); // IE9 only
          transform: translate(@x, @y);
}
.skew(@x; @y) {
  -webkit-transform: skew(@x, @y);
      -ms-transform: skewX(@x) skewY(@y); // See https://github.com/twbs/bootstrap/issues/4885; IE9+
          transform: skew(@x, @y);
}
.translate3d(@x; @y; @z) {
  -webkit-transform: translate3d(@x, @y, @z);
          transform: translate3d(@x, @y, @z);
}

.rotateX(@degrees) {
  -webkit-transform: rotateX(@degrees);
      -ms-transform: rotateX(@degrees); // IE9 only
          transform: rotateX(@degrees);
}
.rotateY(@degrees) {
  -webkit-transform: rotateY(@degrees);
      -ms-transform: rotateY(@degrees); // IE9 only
          transform: rotateY(@degrees);
}
.perspective(@perspective) {
  -webkit-perspective: @perspective;
     -moz-perspective: @perspective;
          perspective: @perspective;
}
.perspective-origin(@perspective) {
  -webkit-perspective-origin: @perspective;
     -moz-perspective-origin: @perspective;
          perspective-origin: @perspective;
}
.transform-origin(@origin) {
  -webkit-transform-origin: @origin;
     -moz-transform-origin: @origin;
      -ms-transform-origin: @origin; // IE9 only
          transform-origin: @origin;
}

Animations

A single mixin for using all of CSS3's animation properties in one declaration and other mixins for individual properties.

The mixins are deprecated as of v3.2.0, with the introduction of Autoprefixer. To preserve backwards-compatibility, Bootstrap will continue to use the mixins internally until Bootstrap v4.

.animation(@animation) {
  -webkit-animation: @animation;
          animation: @animation;
}
.animation-name(@name) {
  -webkit-animation-name: @name;
          animation-name: @name;
}
.animation-duration(@duration) {
  -webkit-animation-duration: @duration;
          animation-duration: @duration;
}
.animation-timing-function(@timing-function) {
  -webkit-animation-timing-function: @timing-function;
          animation-timing-function: @timing-function;
}
.animation-delay(@delay) {
  -webkit-animation-delay: @delay;
          animation-delay: @delay;
}
.animation-iteration-count(@iteration-count) {
  -webkit-animation-iteration-count: @iteration-count;
          animation-iteration-count: @iteration-count;
}
.animation-direction(@direction) {
  -webkit-animation-direction: @direction;
          animation-direction: @direction;
}

Opacity

Set the opacity for all browsers and provide a filter fallback for IE8.

.opacity(@opacity) {
  opacity: @opacity;
  // IE8 filter
  @opacity-ie: (@opacity * 100);
  filter: ~"alpha(opacity=@{opacity-ie})";
}

Placeholder text

Provide context for form controls within each field.

.placeholder(@color: @input-color-placeholder) {
  &::-moz-placeholder           { color: @color; } // Firefox
  &:-ms-input-placeholder       { color: @color; } // Internet Explorer 10+
  &::-webkit-input-placeholder  { color: @color; } // Safari and Chrome
}

Columns

Generate columns via CSS within a single element.

.content-columns(@width; @count; @gap) {
  -webkit-column-width: @width;
     -moz-column-width: @width;
          column-width: @width;
  -webkit-column-count: @count;
     -moz-column-count: @count;
          column-count: @count;
  -webkit-column-gap: @gap;
     -moz-column-gap: @gap;
          column-gap: @gap;
}

Gradients

Easily turn any two colors into a background gradient. Get more advanced and set a direction, use three colors, or use a radial gradient. With a single mixin you get all the prefixed syntaxes you'll need.

#gradient > .vertical(#333; #000);
#gradient > .horizontal(#333; #000);
#gradient > .radial(#333; #000);

You can also specify the angle of a standard two-color, linear gradient:

#gradient > .directional(#333; #000; 45deg);

If you need a barber-stripe style gradient, that's easy, too. Just specify a single color and we'll overlay a translucent white stripe.

#gradient > .striped(#333; 45deg);

Up the ante and use three colors instead. Set the first color, the second color, the second color's color stop (a percentage value like 25%), and the third color with these mixins:

#gradient > .vertical-three-colors(#777; #333; 25%; #000);
#gradient > .horizontal-three-colors(#777; #333; 25%; #000);

Heads up! Should you ever need to remove a gradient, be sure to remove any IE-specific filter you may have added. You can do that by using the .reset-filter() mixin alongside background-image: none;.

Utility mixins

Utility mixins are mixins that combine otherwise unrelated CSS properties to achieve a specific goal or task.

Clearfix

Forget adding class="clearfix" to any element and instead add the .clearfix() mixin where appropriate. Uses the micro clearfix from Nicolas Gallagher.

// Mixin
.clearfix() {
  &:before,
  &:after {
    content: " ";
    display: table;
  }
  &:after {
    clear: both;
  }
}

// Usage
.container {
  .clearfix();
}

Horizontal centering

Quickly center any element within its parent. Requires width or max-width to be set.

// Mixin
.center-block() {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

// Usage
.container {
  width: 940px;
  .center-block();
}

Sizing helpers

Specify the dimensions of an object more easily.

// Mixins
.size(@width; @height) {
  width: @width;
  height: @height;
}
.square(@size) {
  .size(@size; @size);
}

// Usage
.image { .size(400px; 300px); }
.avatar { .square(48px); }

Resizable textareas

Easily configure the resize options for any textarea, or any other element. Defaults to normal browser behavior (both).

.resizable(@direction: both) {
  // Options: horizontal, vertical, both
  resize: @direction;
  // Safari fix
  overflow: auto;
}

Truncating text

Easily truncate text with an ellipsis with a single mixin. Requires element to be block or inline-block level.

// Mixin
.text-overflow() {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

// Usage
.branch-name {
  display: inline-block;
  max-width: 200px;
  .text-overflow();
}

Retina images

Specify two image paths and the @1x image dimensions, and Bootstrap will provide an @2x media query. If you have many images to serve, consider writing your retina image CSS manually in a single media query.

.img-retina(@file-1x; @file-2x; @width-1x; @height-1x) {
  background-image: url("@{file-1x}");

  @media
  only screen and (-webkit-min-device-pixel-ratio: 2),
  only screen and (   min--moz-device-pixel-ratio: 2),
  only screen and (     -o-min-device-pixel-ratio: 2/1),
  only screen and (        min-device-pixel-ratio: 2),
  only screen and (                min-resolution: 192dpi),
  only screen and (                min-resolution: 2dppx) {
    background-image: url("@{file-2x}");
    background-size: @width-1x @height-1x;
  }
}

// Usage
.jumbotron {
  .img-retina("/img/bg-1x.png", "/img/bg-2x.png", 100px, 100px);
}

While Bootstrap is built on Less, it also has an official Sass port. We maintain it in a separate GitHub repository and handle updates with a conversion script.

What's included

Since the Sass port has a separate repo and serves a slightly different audience, the contents of the project differ greatly from the main Bootstrap project. This ensures the Sass port is as compatible with as many Sass-based systems as possible.

Path	Description
`lib/`	Ruby gem code (Sass configuration, Rails and Compass integrations)
`tasks/`	Converter scripts (turning upstream Less to Sass)
`test/`	Compilation tests
`templates/`	Compass package manifest
`vendor/assets/`	Sass, JavaScript, and font files
`Rakefile`	Internal tasks, such as rake and convert

Visit the Sass port's GitHub repository to see these files in action.

Installation

For information on how to install and use Bootstrap for Sass, consult the GitHub repository readme. It's the most up to date source and includes information for use with Rails, Compass, and standard Sass projects.

Bootstrap for Sass

CSS

概述

HTML5 doctype

移动优先

排版和链接

Normalize.css

容器

网格系统

介绍

媒体查询

网格选项

示例：堆叠到水平

示例：流体容器

示例：移动和桌面

示例：移动、平板、桌面

示例：列换行

响应式列重置

偏移列

嵌套列

列排序

Less混合器和变量

变量

混合器

Example usage

排版

标题

h1. Bootstrap heading

h2. Bootstrap heading

h3. Bootstrap heading

h4. Bootstrap heading

h5. Bootstrap heading

h6. Bootstrap heading

h1. Bootstrap heading Secondary text

h2. Bootstrap heading Secondary text

h3. Bootstrap heading Secondary text

h4. Bootstrap heading Secondary text

h5. Bootstrap heading Secondary text

h6. Bootstrap heading Secondary text

正文副本

引导正文副本

使用Less构建

内联文本元素

标记文本

删除文本

删除线文本

插入文本

下划线文本

小文本

粗体

斜体

替代元素

对齐类

变换类

缩写

基本缩写

首字母缩略词

地址

引用块

默认引用块

引用块选项

命名来源

替代显示

列表

无序

有序

无样式

内联

描述

水平描述

自动截断

代码

内联

用户输入

基本块

变量

示例输出

表格

基本示例

条纹行

跨浏览器兼容性

Demo `:focus` state

Caveat about link functionality of `<a>`

Optional icons with hidden `.sr-only` labels