# Overview

Get the lowdown on the key pieces of Bootstrap's infrastructure, including our approach to better, faster, stronger web development.

### HTML5 doctype

Bootstrap makes use of certain HTML elements and CSS properties that require the use of the HTML5 doctype. Include it at the beginning of all your projects.

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

### Mobile first

With Bootstrap 2, we added optional mobile friendly styles for key aspects of the framework. With Bootstrap 3, we've rewritten the project to be mobile friendly from the start. Instead of adding on optional mobile styles, they're baked right into the core. In fact, Bootstrap is mobile first. Mobile first styles can be found throughout the entire library instead of in separate files.

To ensure proper rendering and touch zooming, add the viewport meta tag to your `<head>`.

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

You can disable zooming capabilities on mobile devices by adding `user-scalable=no` to the viewport meta tag. This disables zooming, meaning users are only able to scroll, and results in your site feeling a bit more like a native application. Overall, we don't recommend this on every site, so use caution!

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

### Typography and links

Bootstrap sets basic global display, typography, and link styles. Specifically, we:

- Set `background-color: #fff;` on the `body`
- Use the `@font-family-base`, `@font-size-base`, and `@line-height-base` attributes as our typographic base
- Set the global link color via `@link-color` and apply link underlines only on `:hover`

These styles can be found within `scaffolding.less`.

### Normalize.css

For improved cross-browser rendering, we use Normalize.css, a project by Nicolas Gallagher and Jonathan Neal.

### Containers

Bootstrap requires a containing element to wrap site contents and house our grid system. You may choose one of two containers to use in your projects. Note that, due to `padding` and more, neither container is nestable.

Use `.container` for a responsive fixed width container.

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

Use `.container-fluid` for a full width container, spanning the entire width of your viewport.

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

# Grid system

Bootstrap includes a responsive, mobile first fluid grid system that appropriately scales up to 12 columns as the device or viewport size increases. It includes predefined classes for easy layout options, as well as powerful mixins for generating more semantic layouts.

### Introduction

Grid systems are used for creating page layouts through a series of rows and columns that house your content. Here's how the Bootstrap grid system works:

- Rows must be placed within a `.container` (fixed-width) or `.container-fluid` (full-width) for proper alignment and padding.
- Use rows to create horizontal groups of columns.
- Content should be placed within columns, and only columns may be immediate children of rows.
- Predefined grid classes like `.row` and `.col-xs-4` are available for quickly making grid layouts. Less mixins can also be used for more semantic layouts.
- Columns create gutters (gaps between column content) via `padding`. That padding is offset in rows for the first and last column via negative margin on `.row`s.
- The negative margin is why the examples below are outdented. It's so that content within grid columns is lined up with non-grid content.
- Grid columns are created by specifying the number of twelve available columns you wish to span. For example, three equal columns would use three `.col-xs-4`.
- If more than 12 columns are placed within a single row, each group of extra columns will, as one unit, wrap onto a new line.
- Grid classes apply to devices with screen widths greater than or equal to the breakpoint sizes, and override grid classes targeted at smaller devices. Therefore, applying any `.col-md-` class to an element will not only affect its styling on medium devices but also on large devices if a `.col-lg-` class is not present.

Look to the examples for applying these principles to your code.

### Media queries

We use the following media queries in our Less files to create the key breakpoints in our grid system.

    /* 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) { ... }

We occasionally expand on these media queries to include a `max-width` to limit CSS to a narrower set of devices.

    @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) { ... }

### Grid options

See how aspects of the Bootstrap grid system work across multiple devices with a handy table.

| Extra small devices Phones (<768px) | Small devices Tablets (≥768px) | Medium devices Desktops (≥992px) | Large devices Desktops (≥1200px)
--- | --- | --- | --- | ---
Grid behavior | Horizontal at all times | Collapsed to start, horizontal above breakpoints
Container width | None (auto) | 750px | 970px | 1170px
Class prefix | `.col-xs-` | `.col-sm-` | `.col-md-` | `.col-lg-`
# of columns | 12
Column width | Auto | ~62px | ~81px | ~97px
Gutter width | 30px (15px on each side of a column)
Nestable | Yes
Offsets | Yes
Column ordering | Yes

### Example: Stacked-to-horizontal

Using a single set of `.col-md-*` grid classes, you can create a basic grid system that starts out stacked on mobile devices and tablet devices (the extra small to small range) before becoming horizontal on desktop (medium) devices. Place grid columns in any `.row`.

.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-1
.col-md-8
.col-md-4
.col-md-4
.col-md-4
.col-md-4
.col-md-6
.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>

### Example: Fluid container

Turn any fixed-width grid layout into a full-width layout by changing your outermost `.container` to `.container-fluid`.

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

### Example: Mobile and desktop

Don't want your columns to simply stack in smaller devices? Use the extra small and medium device grid classes by adding `.col-xs-*` `.col-md-*` to your columns. See the example below for a better idea of how it all works.

.col-xs-12 .col-md-8
.col-xs-6 .col-md-4
.col-xs-6 .col-md-4
.col-xs-6 .col-md-4
.col-xs-6 .col-md-4
.col-xs-6
.col-xs-6

    <!-- Stack the columns on mobile by making one full-width and the other half-width -->
    <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>

    <!-- Columns start at 50% wide on mobile and bump up to 33.3% wide on desktop -->
    <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>

    <!-- Columns are always 50% wide, on mobile and desktop -->
    <div class="row">
      <div class="col-xs-6">.col-xs-6</div>
      <div class="col-xs-6">.col-xs-6</div>
    </div>

### Example: Mobile, tablet, desktops

Build on the previous example by creating even more dynamic and powerful layouts with tablet `.col-sm-*` classes.

.col-xs-12 .col-sm-6 .col-md-8
.col-xs-6 .col-md-4
.col-xs-6 .col-sm-4
.col-xs-6 .col-sm-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>
      <!-- Optional: clear the XS cols if their content doesn't match in height -->
      <div class="clearfix visible-xs-block"></div>
      <div class="col-xs-6 col-sm-4">.col-xs-6 .col-sm-4</div>
    </div>

### Example: Column wrapping

If more than 12 columns are placed within a single row, each group of extra columns will, as one unit, wrap onto a new line.

.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>

### Responsive column resets

With the four tiers of grids available you're bound to run into issues where, at certain breakpoints, your columns don't clear quite right as one is taller than the other. To fix that, use a combination of a `.clearfix` and our responsive utility classes.

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

      <!-- Add the extra clearfix for only the required viewport -->
      <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>

In addition to column clearing at responsive breakpoints, you may need to reset offsets, pushes, or pulls. See this in action in the grid example.

    <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>

### Offsetting columns

Move columns to the right using `.col-md-offset-*` classes. These classes increase the left margin of a column by `*` columns. For example, `.col-md-offset-4` moves `.col-md-4` over four columns.

.col-md-4
.col-md-4 .col-md-offset-4
.col-md-3 .col-md-offset-3
.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>

### Nesting columns

To nest your content with the default grid, add a new `.row` and set of `.col-sm-*` columns within an existing `.col-sm-*` column. Nested rows should include a set of columns that add up to 12 or less (it is not required that you use all 12 available columns).

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>

### Column ordering

Easily change the order of our built-in grid columns with `.col-md-push-*` and `.col-md-pull-*` modifier classes.

.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 mixins and variables

In addition to prebuilt grid classes for fast layouts, Bootstrap includes Less variables and mixins for quickly generating your own simple, semantic layouts.

#### Variables

Variables determine the number of columns, the gutter width, and the media query point at which to begin floating columns. We use these to generate the predefined grid classes documented above, as well as for the custom mixins listed below.

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

#### Mixins

Mixins are used in conjunction with the grid variables to generate semantic CSS for individual grid columns.

    // Creates a wrapper for a series of columns
    .make-row(@gutter: @grid-gutter-width) {
      // Then clear the floated columns
      .clearfix();

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

      // Negative margin nested rows out to align the content of columns
      .row {
        margin-left:  (@gutter / -2);
        margin-right: (@gutter / -2);
      }
    }

    // Generate the extra small columns
    .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>

# Typography

## Headings

All HTML headings, `<h1>` through `<h6>`, are available. `.h1` through `.h6` classes are also available, for when you want to match the font styling of a heading but still want your text to be displayed inline.

# 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>

Create lighter, secondary text in any heading with a generic `<small>` tag or the `.small` class.

# 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>

## Body copy

Bootstrap's global default `font-size` is 14px, with a `line-height` of 1.428. This is applied to the `<body>` and all paragraphs. In addition, `<p>` (paragraphs) receive a bottom margin of half their computed line-height (10px by default).

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>

### Lead body copy

Make a paragraph stand out by adding `.lead`.

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

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

### Built with Less

The typographic scale is based on two Less variables in variables.less: `@font-size-base` and `@line-height-base`. The first is the base font-size used throughout and the second is the base line-height. We use those variables and some simple math to create the margins, paddings, and line-heights of all our type and more. Customize them and Bootstrap adapts.

## Inline text elements

### Marked text

For highlighting a run of text due to its relevance in another context, use the `<mark>` tag.

You can use the mark tag to highlight text.

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

### Deleted text

For indicating blocks of text that have been deleted use the `<del>` tag.

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>

### Strikethrough text

For indicating blocks of text that are no longer relevant use the `<s>` tag.

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>

### Inserted text

For indicating additions to the document use the `<ins>` tag.

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>

### Underlined text

To underline text use the `<u>` tag.

This line of text will render as underlined

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

Make use of HTML's default emphasis tags with lightweight styles.

### Small text

For de-emphasizing inline or blocks of text, use the `<small>` tag to set text at 85% the size of the parent. Heading elements receive their own `font-size` for nested `<small>` elements.

You may alternatively use an inline element with `.small` in place of any `<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>

### Bold

For emphasizing a snippet of text with a heavier font-weight.

The following snippet of text is rendered as bold text.

    <strong>rendered as bold text</strong>

### Italics

For emphasizing a snippet of text with italics.

The following snippet of text is rendered as italicized text.

    <em>rendered as italicized text</em>

#### Alternate elements

Feel free to use `<b>` and `<i>` in HTML5. `<b>` is meant to highlight words or phrases without conveying additional importance while `<i>` is mostly for voice, technical terms, etc.

## Alignment classes

Easily realign text to components with text alignment classes.

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>

## Transformation classes

Transform text in components with text capitalization classes.

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>

## Abbreviations

Stylized implementation of HTML's `<abbr>` element for abbreviations and acronyms to show the expanded version on hover. Abbreviations with a `title` attribute have a light dotted bottom border and a help cursor on hover, providing additional context on hover.

### Basic abbreviation

For expanded text on long hover of an abbreviation, include the `title` attribute with the `<abbr>` element.

An abbreviation of the word attribute is attr.

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

### Initialism

Add `.initialism` to an abbreviation for a slightly smaller font-size.

HTML is the best thing since sliced bread.

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

## Addresses

Present contact information for the nearest ancestor or the entire body of work. Preserve formatting by ending all lines with `<br>`.

    <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>

## Blockquotes

For quoting blocks of content from another source within your document.

### Default blockquote

Wrap `<blockquote>` around any HTML as the quote. For straight quotes, we recommend a `<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>

### Blockquote options

Style and content changes for simple variations on a standard `<blockquote>`.

#### Naming a source

Add a `<footer>` for identifying the source. Wrap the name of the source work in `<cite>`.

> 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>
      <footer>Someone famous in <cite title="Source Title">Source Title</cite></footer>
    </blockquote>

#### Alternate displays

Add `.blockquote-reverse` for a blockquote with right-aligned content.

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

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

## Lists

### Unordered

A list of items in which the order does not explicitly matter.

- 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>

### Ordered

A list of items in which the order does explicitly matter.

1. Lorem ipsum dolor sit amet
2. Consectetur adipiscing elit
3. Integer molestie lorem at massa
4. Facilisis in pretium nisl aliquet
5. Nulla volutpat aliquam velit
6. Faucibus porta lacus fringilla vel
7. Aenean sit amet erat nunc
8. Eget porttitor lorem

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

### Unstyled

Remove the default `list-style` and left margin on list items (immediate children only). This only applies to immediate children list items, meaning you will need to add the class for any nested lists as well.

- 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>

### Inline

Place all list items on a single line with `display: inline-block;` and some light padding.

- Lorem ipsum
- Phasellus iaculis
- Nulla volutpat

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

### Description

A list of terms with their associated descriptions.

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>

#### Horizontal description

Make terms and descriptions in `<dl>` line up side-by-side. Starts off stacked like default `<dl>`s, but when the navbar expands, so do these.

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>

#### Auto-truncating

Horizontal description lists will truncate terms that are too long to fit in the left column with `text-overflow`. In narrower viewports, they will change to the default stacked layout.

# Code

## Inline

Wrap inline snippets of code with `<code>`.

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

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

## User input

Use the `<kbd>` to indicate input that is typically entered via keyboard.

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>

## Basic block

Use `<pre>` for multiple lines of code. Be sure to escape any angle brackets in the code for proper rendering.

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

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

You may optionally add the `.pre-scrollable` class, which will set a max-height of 350px and provide a y-axis scrollbar.

## Variables

For indicating variables use the `<var>` tag.

y = m x + b

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

## Sample output

For indicating blocks sample output from a program use the `<samp>` tag.

`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>

# Tables

## Basic example

For basic styling—light padding and only horizontal dividers—add the base class `.table` to any `<table>`. It may seem super redundant, but given the widespread use of tables for other plugins like calendars and date pickers, we've opted to isolate our custom table styles.

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>

## Striped rows

Use `.table-striped` to add zebra-striping to any table row within the `<tbody>`.

#### Cross-browser compatibility

Striped tables are styled via the `:nth-child` CSS selector, which is not available in Internet Explorer 8.

# | 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
Mark | Otto | @TwBootstrap
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>

## 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.

#### 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>

# Forms

## 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.

Email address
Password
File input

Example block-level help text here.

Check me out

    <form role="form">
      <div class="form-group">
        <label for="exampleInputEmail1">Email address</label>
        <input type="email" class="form-control" id="exampleInputEmail1" placeholder="Enter 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>` for left-aligned and inline-block controls. This only applies to forms within viewports that are at least 768px wide.

#### Requires 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.

Email address
@
Password
Remember me

    <form class="form-inline" role="form">
      <div class="form-group">
        <label class="sr-only" for="exampleInputEmail2">Email address</label>
        <input type="email" class="form-control" id="exampleInputEmail2" placeholder="Enter email">
      </div>
      <div class="form-group">
        <div class="input-group">
          <div class="input-group-addon">@</div>
          <input class="form-control" type="email" placeholder="Enter email">
        </div>
      </div>
      <div class="form-group">
        <label class="sr-only" for="exampleInputPassword2">Password</label>
        <input type="password" class="form-control" id="exampleInputPassword2" 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>

## 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. Doing so changes `.form-group`s to behave as grid rows, so no need for `.row`.

Email
Password
Remember me

    <form class="form-horizontal" role="form">
      <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)

Option one is this and that—be sure to include why it's great
Option two is disabled
Option one is this and that—be sure to include why it's great
Option two can be something else and selecting it will deselect option one
Option three is disabled

    <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.

1 2 3
1 2 3

    <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 labels

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.

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

### Selects

Use the default option, or add `multiple` to show multiple options at once.

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

    <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>`.

Email

email@example.com

Password

    <form class="form-horizontal" role="form">
      <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>

Email

email@example.com

Password

    <form class="form-inline" role="form">
      <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>

## Input focus

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 inputs

Add the `disabled` boolean attribute on an input to prevent user input and trigger a slightly different look.

    <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>`

Our styles use `pointer-events: none` to try to disable the link functionality of `<a class="btn btn-*">` buttons in this case, but that CSS property is not yet standardized and isn't fully supported in Opera 18 and below, or in Internet Explorer 11. 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.

Disabled input
Disabled select menu
Can't check this

    <form role="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 inputs

Add the `readonly` boolean attribute on an input to prevent user input and style the input as disabled.

    <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.

Input with success
Input with warning
Input with error
Checkbox with success
Checkbox with warning
Checkbox with error

    <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.

Input with success
Input with warning
Input with error

    <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">
      <span class="glyphicon glyphicon-ok form-control-feedback"></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">
      <span class="glyphicon glyphicon-warning-sign form-control-feedback"></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">
      <span class="glyphicon glyphicon-remove form-control-feedback"></span>
    </div>

#### Optional icons in horizontal and inline forms

Input with success

    <form class="form-horizontal" role="form">
      <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">
          <span class="glyphicon glyphicon-ok form-control-feedback"></span>
        </div>
      </div>
    </form>

Input with success

    <form class="form-inline" role="form">
      <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">
        <span class="glyphicon glyphicon-ok form-control-feedback"></span>
      </div>
    </form>

#### Optional icons with hidden `.sr-only` labels

For form controls with no visible label, add the `.sr-only` class on the label. Bootstrap will automatically adjust the position of the icon once it's been added.

Hidden label

    <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">
      <span class="glyphicon glyphicon-ok form-control-feedback"></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`.

Large label
Small label

    <form class="form-horizontal" role="form">
      <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.

A block of help text that breaks onto a new line and may extend beyond one line.

    <span class="help-block">A block of help text that breaks onto a new line and may extend beyond one line.</span>

# Buttons

## 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>

## 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 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. So to be safe, use custom JavaScript to disable such links.

#### 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.

## Button tags

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

Link

    <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">

#### 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.

# Images

## Responsive images

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

#### 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.

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

# Helper classes

### 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.

### 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.

### Close icon

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

    <button type="button" class="close"><span aria-hidden="true">&times;</span><span class="sr-only">Close</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();
    }

#### Not for use in navbars

To align components in navbars with utility classes, use `.navbar-left` or `.navbar-right` instead. See the navbar docs for details.

### Center content blocks

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

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

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

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

### Clearfix

Easily clear `float`s 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;
      visibility: hidden !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();
    }

# Responsive utilities

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

# Using Less

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: #428bca;
    @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 type face, 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 Gallager.

    // 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);
    }

# Using Sass

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