Global CSS settings, fundamental HTML elements styled and enhanced with extensible classes, and an advanced grid system.
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.
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>.
You can disable zooming capabilities on mobile devices by adding user-scalable=noto 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!
Typography and links
Bootstrap sets basic global display, typography, and link styles. Specifically, we
Set background-color: #fff;on thebody
Use the @font-family-base, @font-size-base, and @line-height-baseattributes as our typographic base
Set the global link color via @link-colorand apply link underlines only on:hover
These styles can be found within scaffolding.less.
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 paddingand more, neither container is nestable.
Use .containerfor a responsive fixed width container.
Use .container-fluidfor a full width container, spanning the entire width of your viewport.
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 .rowand .col-xs-4are 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 .rows.
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, eg 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.
We occasionally expand on these media queries to include a max-widthto limit CSS to a narrower set of devices.
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
Example: Fluid container
Turn any fixed-width grid layout into a full-width layout by changing your outermost .containerto .container-fluid.
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
Example: Mobile, tablet, desktop
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
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.
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 .clearfixand 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
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 .
Remove gutters
Remove the gutters from a row and it's columns with the .row-no-guttersclass.
.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
offset 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-4moves .col-md-4over 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
You can also override offsets from lower grid tiers with .col-*-offset-0classes.
Nesting columns
To nest your content with the default grid, add a new .rowand 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 fewer (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
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
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.
Mixins
Mixins are used in conjunction with the grid variables to generate semantic CSS for individual 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.
Typography
headings
All HTML headings, <h1>through <h6>, are available. .h1through .h6classes 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
Create lighter, secondary text in any heading with a generic <small>tag or the .smallclass.
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
body copy
Bootstrap's global default font-sizeis 14px , with a line-heightof 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.
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.
Built with Less
The typographic scale is based on two Less variables in variables.less : @font-size-baseand @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 tohighlighttext.
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.
Strike through 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.
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.
underlined text
To underline text use the <u>tag.
This line of text will render as underlined
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-sizefor nested <small>elements.
You may alternatively use an inline element with .smallin place of any <small>.
This line of text is meant to be treated as fine print.
Bold
For emphasizing a snippet of text with a heavy font-weight.
The following snippet of text is rendered as bold text .
Italics
For emphasizing a snippet of text with italics.
The following snippet of text is rendered as italicized text .
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.
Transformation classes
Transform text in components with text capitalization classes.
lowercased text.
uppercased text.
capitalized text.
Abbreviations
Stylized implementation of HTML's <abbr>element for abbreviations and acronyms to show the expanded version on hover. Abbreviations with a titleattribute have a light dotted bottom border and a help cursor on hover, providing additional context on hover and to users of assistive technologies.
Basic abbreviation
An abbreviation of the word attribute is attr .
initialism
Add .initialismto an abbreviation for a slightly smaller font-size.
HTML is the best thing since sliced bread.
Addresses
Present contact information for the nearest ancestor or the entire body of work. Preserve formatting by ending all lines with <br>.
Twitter Inc. 1355 Market Street, Suite 900 San Francisco, CA 94103 P: (123) 456-7890
Full Name [email protected]
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 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.
Alternate displays
Add .blockquote-reversefor a blockquote with right-aligned content.
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.
Lists
Unordered
A list of items in which the order does not explicitly matter.
Lorem ipsum dolor sit amet
Consectetur adipiscing elite
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
ordered
A list of items in which the order does explicitly matter.
Lorem ipsum dolor sit amet
Consectetur adipiscing elite
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
unstyled
Remove the default list-styleand 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 elite
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
Inline
Place all list items on a single line with display: inline-block;and some light padding.
Lorem ipsum
Phasellus iaculis
Nulla volutpat
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.
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 ametrisus.
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.
user input
Use the <kbd>to indicate input that is typically entered via keyboard.
To switch directories, type
cdfollowed by the name of the directory.
To edit settings, press
ctrl + ,
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>
You may optionally add the .pre-scrollableclass, 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
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.
tables
basic example
For basic styling—light padding and only horizontal dividers—add the base class .tableto 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
one
Mark
Otto
@mdo
2
Jacob
Thornton
@fat
3
Larry
the Bird
@twitter
striped rows
Use .table-stripedto add zebra-striping to any table row within the <tbody>.
Cross-browser compatibility
Striped tables are styled via the :nth-childCSS selector, which is not available in Internet Explorer 8.
#
first name
last name
username
one
Mark
Otto
@mdo
2
Jacob
Thornton
@fat
3
Larry
the Bird
@twitter
bordered table
Add .table-borderedfor borders on all sides of the table and cells.
#
first name
last name
username
one
Mark
Otto
@mdo
2
Jacob
Thornton
@fat
3
Larry
the Bird
@twitter
hover rows
Add .table-hoverto enable a hover state on table rows within a <tbody>.
#
first name
last name
username
one
Mark
Otto
@mdo
2
Jacob
Thornton
@fat
3
Larry
the Bird
@twitter
Condensed table
Add .table-condensedto make tables more compact by cutting cell padding in half.
#
first name
last name
username
one
Mark
Otto
@mdo
2
Jacob
Thornton
@fat
3
Larry the Bird
@twitter
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
one
Column content
Column content
Column content
2
Column content
Column content
Column content
3
Column content
Column content
Column content
four
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
eight
Column content
Column content
Column content
9
Column content
Column content
Column content
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-onlyclass.
Responsive tables
Create responsive tables by wrapping any .tablein .table-responsiveto 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 widththat interferes with the responsive table. This cannot be overridden without a Firefox-specific hack that we don't provide in Bootstrap:
Individual form controls automatically receive some global styling. All textual <input>, <textarea>, and <select>elements with .form-controlare set to width: 100%;by default. Wrap labels and controls in .form-groupfor optimum spacing.
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-inlineto 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-onlyclass. There are further alternative methods of providing a label for assistive technologies, such as the aria-label, aria-labelledbyor titleattribute. If none of these is present, screen readers may resort to using the placeholderattribute, if present, but note that use of placeholderas a replacement for other labeling methods is not advised.
horizontal form
Use Bootstrap's predefined grid classes to align labels and groups of form controls in a horizontal layout by adding .form-horizontalto the form (which doesn't have to be a <form>). Doing so changes .form-groupto behave as grid rows, so no need for .row.
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 typeis properly declared.
Form control which supports multiple lines of text. Change rowsattribute as necessary.
Checkboxes and radios
Checkboxes are for selecting one or several options in a list, while radios are for selecting one option from many.
Disabled checkboxes and radios are supported, but to provide a "not-allowed" cursor on hover of the parent <label>, you'll need to add the .disabledclass to the parent .radio, .radio-inline, .checkbox, or .checkbox-inline.
default (stacked)
Inline checkboxes and radios
Use the .checkbox-inlineor .radio-inlineclasses on a series of checkboxes or radios for controls that appear on the same line.
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).
Selects
Note that many native select menus—namely in Safari and Chrome—have rounded corners that cannot be modified via border-radiusproperties.
For <select>controls with the multipleattribute, multiple options are shown by default.
static control
When you need to place plain text next to a form label within a form, use the .form-control-staticclass on a <p>.
focus state
We remove the default outlinestyles on some form controls and apply a box-shadowin its place for :focus.
demo :focusstate
The above example input uses custom styles in our documentation to demonstrate the :focusstate on a .form-control.
disabled state
Add the disabledboolean attribute on an input to prevent user interactions. Disabled inputs appear lighter and add a not-allowedcursor.
Disabled fieldsets
Add the disabledattribute 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 '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 disabledattribute on a <fieldset>. Use custom JavaScript to disable the fieldset in these browsers.
Readonly state
Add the readonlyboolean 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.
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-describedbyattribute. This will ensure that assistive technologies – such as screen readers – will announce this help text when the user focuses or enters the control.
Validation states
Bootstrap includes validation styles for error, warning, and success states on form controls. To use, add .has-warning, .has-error, or .has-successto the parent element. Any .control-label, .form-control, and .help-blockwithin 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-onlyclass - 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.
With optional icons
You can also add optional feedback icons with the addition of .has-feedbackand 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-onlyclass. If you must do without labels, adjust the topvalue of the feedback icon. For input groups, adjust the rightvalue 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-onlyclass 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-onlytext and aria-describedby) has been included for illustrative purposes.
Optional icons in horizontal and inline forms
Optional icons with hidden .sr-onlylabels
If you use the .sr-onlyclass to hide a form control's <label>(rather than using other labeling options, such as the aria-labelattribute), Bootstrap will automatically adjust the position of the icon once it's been added.
(success)
@
(success)
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.
horizontal form group sizes
Quickly size labels and form controls within .form-horizontalby adding .form-group-lgor .form-group-sm.
Column sizing
Wrap inputs in grid columns, or any custom parent element, to easily enforce desired widths.
Buttons
Button tags
Use the button classes on an <a>, <button>, or <input>element.
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-heightof <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.
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-onlyclass.
Sizes
Fancy larger or smaller buttons? Add .btn-lg, .btn-sm, or .btn-xsfor additional sizes.
Create block level buttons—those that span the full width of a parent—by adding .btn-block.
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 .activeon <button>s (and include thearia-pressed="true" attribute) should you need to replicate the active state programmatically.
button element
No need to add :activeas it's a pseudo-class, but if you need to force the same appearance, go ahead and add .active.
We use .disabledas a utility class here, similar to the common .activeclass, so no prefix is required.
Link functionality
This class uses pointer-events: noneto 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.
images
Responsive images
Images in Bootstrap 3 can be made responsive-friendly via the addition of the .img-responsiveclass. 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-responsiveclass, use .center-blockinstead of .text-center. See the helper classes section for more details about .center-blockusage.
SVG images and IE 8-10
In Internet Explorer 8-10, SVG images with .img-responsiveare 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.
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.
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.
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-onlyclass .
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.
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 is 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.
carriages
Use carets to indicate dropdown functionality and direction. Note that the default caret will reverse automatically in dropup menus .
Quick floats
Float an element to the left or right with a class. !importantis included to avoid specificity issues. Classes can also be used as mixins.
Not for use in navbars
To align components in navbars with utility classes, use .navbar-leftor .navbar-rightinstead. See the navbar docs for details.
Center content blocks
Set an element to display: blockand center via margin. Available as a mixin and class.
Clearfix
Easily clear floats by adding .clearfixto the parent element . Utilizes the micro clearfix as popularized by Nicolas Gallagher. Can also be used as a mixin.
Showing and hiding content
Force an element to be shown or hidden ( including for screen readers ) with the use of .showand .hiddenclasses. These classes use !importantto avoid specificity conflicts, just like the quick floats . They are only available for block level toggling. They can also be used as mixins.
.hideis available, but it does not always affect screen readers and is deprecated as of v3.0.1. Use .hiddenor .sr-onlyinstead.
Furthermore, .invisiblecan be used to toggle only the visibility of an element, meaning its displayis not modified and the element can still affect the flow of the document.
Screen reader and keyboard navigation content
Hide an element to all devices except screen readers with .sr-only. Combine .sr-onlywith .sr-only-focusableto show the element again when it's focused (eg by a keyboard-only user). Necessary for following accessibility best practices . Can also be used as mixins.
Image replacement
Utilize the .text-hideclass or mixin to help replace an element's text content with a background image.
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 displayproperty value listed below.
Group of classes
cssdisplay
.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-lgalso 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.
The class .visible-printalso 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.
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 set up 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
Easy 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.
Use any of these color variables as they are or reassign them to more meaningful variables for your project.
scaffolding
A handful of variables for quickly customizing key elements of your site's skeleton.
Links
Easy style your links with the right color with only one value.
Note that the @link-hover-coloruses 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.
Icons
Two quick variables for customizing the location and filename of your icons.
Components
Components throughout Bootstrap make use of some default variables for setting common values. Here are the most commonly used.
Vendor mixins
Vendor mixins are mixins to help support multiple browsers by including all relevant vendor prefixes in your compiled CSS.
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.
rounded corners
Today all modern browsers support the non-prefixed border-radiusproperty. 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.
Box (Drop) shadows
If your target audience is using the latest and greatest browsers and devices, be sure to just use the box-shadowproperty 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 -webkitprefix.
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.
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.
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.
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.
Opacity
Set the opacity for all browsers and provide a filterfallback for IE8.
placeholder text
Provide context for form controls within each field.
columns
Generate columns via CSS within a single element.
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.
You can also specify the angle of a standard two-color, linear gradient:
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.
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:
Head up! Should you ever need to remove a gradient, be sure to remove any IE-specific filteryou 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 .
horizontal centering
Quickly center any element within its parent. Requires widthor max-widthto be set.
Sizing helpers
Specify the dimensions of an object more easily.
Resizable text areas
Easily configure the resize options for any textarea, or any other element. Defaults to normal browser behavior ( both).
Trunking text
Easily truncate text with an ellipsis with a single mixin. Requires element to be blockor inline-blocklevel.
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.
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)
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.