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<a href="/docs/4.4/components/jumbotron/">
Jumbotron
</a>
</li><li>
<a href="/docs/4.4/components/list-group/">
List group
</a>
</li><li>
<a href="/docs/4.4/components/media-object/">
Media object
</a>
</li><li>
<a href="/docs/4.4/components/modal/">
Modal
</a>
</li><li>
<a href="/docs/4.4/components/navs/">
Navs
</a>
</li><li>
<a href="/docs/4.4/components/navbar/">
Navbar
</a>
</li><li>
<a href="/docs/4.4/components/pagination/">
Pagination
</a>
</li><li>
<a href="/docs/4.4/components/popovers/">
Popovers
</a>
</li><li>
<a href="/docs/4.4/components/progress/">
Progress
</a>
</li><li>
<a href="/docs/4.4/components/scrollspy/">
Scrollspy
</a>
</li><li>
<a href="/docs/4.4/components/spinners/">
Spinners
</a>
</li><li>
<a href="/docs/4.4/components/toasts/">
Toasts
</a>
</li><li>
<a href="/docs/4.4/components/tooltips/">
Tooltips
</a>
</li></ul>
</div><div class="bd-toc-item">
<a class="bd-toc-link" href="/docs/4.4/utilities/borders/">
Utilities
</a>
<ul class="nav bd-sidenav"><li>
<a href="/docs/4.4/utilities/borders/">
Borders
</a>
</li><li>
<a href="/docs/4.4/utilities/clearfix/">
Clearfix
</a>
</li><li>
<a href="/docs/4.4/utilities/close-icon/">
Close icon
</a>
</li><li>
<a href="/docs/4.4/utilities/colors/">
Colors
</a>
</li><li>
<a href="/docs/4.4/utilities/display/">
Display
</a>
</li><li>
<a href="/docs/4.4/utilities/embed/">
Embed
</a>
</li><li>
<a href="/docs/4.4/utilities/flex/">
Flex
</a>
</li><li>
<a href="/docs/4.4/utilities/float/">
Float
</a>
</li><li>
<a href="/docs/4.4/utilities/image-replacement/">
Image replacement
</a>
</li><li>
<a href="/docs/4.4/utilities/overflow/">
Overflow
</a>
</li><li>
<a href="/docs/4.4/utilities/position/">
Position
</a>
</li><li>
<a href="/docs/4.4/utilities/screen-readers/">
Screen readers
</a>
</li><li>
<a href="/docs/4.4/utilities/shadows/">
Shadows
</a>
</li><li>
<a href="/docs/4.4/utilities/sizing/">
Sizing
</a>
</li><li>
<a href="/docs/4.4/utilities/spacing/">
Spacing
</a>
</li><li>
<a href="/docs/4.4/utilities/stretched-link/">
Stretched link
</a>
</li><li>
<a href="/docs/4.4/utilities/text/">
Text
</a>
</li><li>
<a href="/docs/4.4/utilities/vertical-align/">
Vertical align
</a>
</li><li>
<a href="/docs/4.4/utilities/visibility/">
Visibility
</a>
</li></ul>
</div><div class="bd-toc-item">
<a class="bd-toc-link" href="/docs/4.4/extend/approach/">
Extend
</a>
<ul class="nav bd-sidenav"><li>
<a href="/docs/4.4/extend/approach/">
Approach
</a>
</li><li>
<a href="/docs/4.4/extend/icons/">
Icons
</a>
</li></ul>
</div><div class="bd-toc-item">
<a class="bd-toc-link" href="/docs/4.4/migration/">
Migration
</a>
<ul class="nav bd-sidenav"></ul>
</div><div class="bd-toc-item">
<a class="bd-toc-link" href="/docs/4.4/about/overview/">
About
</a>
<ul class="nav bd-sidenav"><li>
<a href="/docs/4.4/about/overview/">
Overview
</a>
</li><li>
<a href="/docs/4.4/about/team/">
Team
</a>
</li><li>
<a href="/docs/4.4/about/brand/">
Brand
</a>
</li><li>
<a href="/docs/4.4/about/license/">
License
</a>
</li><li>
<a href="/docs/4.4/about/translations/">
Translations
</a>
</li></ul>
</div></nav>
</div>
<nav class="d-none d-xl-block col-xl-2 bd-toc" aria-label="Secondary navigation">
<ul class="section-nav">
<li class="toc-entry toc-h2"><a href="#approach">Approach</a></li>
<li class="toc-entry toc-h2"><a href="#page-defaults">Page defaults</a></li>
<li class="toc-entry toc-h2"><a href="#native-font-stack">Native font stack</a></li>
<li class="toc-entry toc-h2"><a href="#headings-and-paragraphs">Headings and paragraphs</a></li>
<li class="toc-entry toc-h2"><a href="#lists">Lists</a></li>
<li class="toc-entry toc-h2"><a href="#preformatted-text">Preformatted text</a></li>
<li class="toc-entry toc-h2"><a href="#tables">Tables</a></li>
<li class="toc-entry toc-h2"><a href="#forms">Forms</a></li>
<li class="toc-entry toc-h2"><a href="#misc-elements">Misc elements</a>
<ul>
<li class="toc-entry toc-h3"><a href="#address">Address</a></li>
<li class="toc-entry toc-h3"><a href="#blockquote">Blockquote</a></li>
<li class="toc-entry toc-h3"><a href="#inline-elements">Inline elements</a></li>
<li class="toc-entry toc-h3"><a href="#summary">Summary</a></li>
</ul>
</li>
<li class="toc-entry toc-h2"><a href="#html5-hidden-attribute">HTML5 [hidden] attribute</a></li>
</ul>
</nav>
<main class="col-md-9 col-xl-8 py-md-3 pl-md-5 bd-content" role="main">
<h1 class="bd-title" id="content">Reboot</h1>
<p class="bd-lead">Reboot, a collection of element-specific CSS changes in a single file, kickstart Bootstrap to provide an elegant, consistent, and simple baseline to build upon.</p>
<script async src="https://cdn.carbonads.com/carbon.js?serve=CKYIKKJL&placement=getbootstrapcom" id="_carbonads_js"></script>
<h2 id="approach">Approach</h2>
<p>Reboot builds upon Normalize, providing many HTML elements with somewhat opinionated styles using only element selectors. Additional styling is done only with classes. For example, we reboot some <code class="highlighter-rouge"><table></code> styles for a simpler baseline and later provide <code class="highlighter-rouge">.table</code>, <code class="highlighter-rouge">.table-bordered</code>, and more.</p>
<p>Here are our guidelines and reasons for choosing what to override in Reboot:</p>
<ul>
<li>Update some browser default values to use <code class="highlighter-rouge">rem</code>s instead of <code class="highlighter-rouge">em</code>s for scalable component spacing.</li>
<li>Avoid <code class="highlighter-rouge">margin-top</code>. Vertical margins can collapse, yielding unexpected results. More importantly though, a single direction of <code class="highlighter-rouge">margin</code> is a simpler mental model.</li>
<li>For easier scaling across device sizes, block elements should use <code class="highlighter-rouge">rem</code>s for <code class="highlighter-rouge">margin</code>s.</li>
<li>Keep declarations of <code class="highlighter-rouge">font</code>-related properties to a minimum, using <code class="highlighter-rouge">inherit</code> whenever possible.</li>
</ul>
<h2 id="page-defaults">Page defaults</h2>
<p>The <code class="highlighter-rouge"><span class="nt"><html></span></code> and <code class="highlighter-rouge"><body></code> elements are updated to provide better page-wide defaults. More specifically:</p>
<ul>
<li>The <code class="highlighter-rouge">box-sizing</code> is globally set on every element—including <code class="highlighter-rouge">*::before</code> and <code class="highlighter-rouge">*::after</code>, to <code class="highlighter-rouge">border-box</code>. This ensures that the declared width of element is never exceeded due to padding or border.</li>
<li>No base <code class="highlighter-rouge">font-size</code> is declared on the <code class="highlighter-rouge"><span class="nt"><html></span></code>, but <code class="highlighter-rouge">16px</code> is assumed (the browser default). <code class="highlighter-rouge">font-size: 1rem</code> is applied on the <code class="highlighter-rouge"><body></code> for easy responsive type-scaling via media queries while respecting user preferences and ensuring a more accessible approach.</li>
<li>The <code class="highlighter-rouge"><body></code> also sets a global <code class="highlighter-rouge">font-family</code>, <code class="highlighter-rouge">line-height</code>, and <code class="highlighter-rouge">text-align</code>. This is inherited later by some form elements to prevent font inconsistencies.</li>
<li>For safety, the <code class="highlighter-rouge"><body></code> has a declared <code class="highlighter-rouge">background-color</code>, defaulting to <code class="highlighter-rouge">#fff</code>.</li>
</ul>
<h2 id="native-font-stack">Native font stack</h2>
<p>The default web fonts (Helvetica Neue, Helvetica, and Arial) have been dropped in Bootstrap 4 and replaced with a “native font stack” for optimum text rendering on every device and OS. Read more about <a href="https://www.smashingmagazine.com/2015/11/using-system-ui-fonts-practical-guide/">native font stacks in this <em>Smashing Magazine</em> article</a>.</p>
<figure class="highlight"><pre><code class="language-sass" data-lang="sass"><span class="nv">$font-family-sans-serif</span><span class="p">:</span>
<span class="c1">// Safari for macOS and iOS (San Francisco)</span>
<span class="nt">-apple-system</span><span class="o">,</span>
<span class="c1">// Chrome < 56 for macOS (San Francisco)</span>
<span class="nt">BlinkMacSystemFont</span><span class="o">,</span>
<span class="c1">// Windows</span>
<span class="s2">"Segoe UI"</span><span class="o">,</span>
<span class="c1">// Android</span>
<span class="s2">"Roboto"</span><span class="o">,</span>
<span class="c1">// Basic web fallback</span>
<span class="s2">"Helvetica Neue"</span><span class="o">,</span> <span class="nt">Arial</span><span class="o">,</span> <span class="nt">sans-serif</span><span class="o">,</span>
<span class="c1">// Emoji fonts</span>
<span class="s2">"Apple Color Emoji"</span><span class="o">,</span> <span class="s2">"Segoe UI Emoji"</span><span class="o">,</span> <span class="s2">"Segoe UI Symbol"</span> <span class="o">!</span><span class="nt">default</span><span class="o">;</span></code></pre></figure>
<p>This <code class="highlighter-rouge">font-family</code> is applied to the <code class="highlighter-rouge"><body></code> and automatically inherited globally throughout Bootstrap. To switch the global <code class="highlighter-rouge">font-family</code>, update <code class="highlighter-rouge">$font-family-base</code> and recompile Bootstrap.</p>
<h2 id="headings-and-paragraphs">Headings and paragraphs</h2>
<p>All heading elements—e.g., <code class="highlighter-rouge"><h1></code>—and <code class="highlighter-rouge"><p></code> are reset to have their <code class="highlighter-rouge">margin-top</code> removed. Headings have <code class="highlighter-rouge">margin-bottom: .5rem</code> added and paragraphs <code class="highlighter-rouge">margin-bottom: 1rem</code> for easy spacing.</p>
<table>
<thead>
<tr>
<th>Heading</th>
<th>Example</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<p><code class="highlighter-rouge"><h1></h1></code></p>
</td>
<td><span class="h1">h1. Bootstrap heading</span></td>
</tr>
<tr>
<td>
<p><code class="highlighter-rouge"><h2></h2></code></p>
</td>
<td><span class="h2">h2. Bootstrap heading</span></td>
</tr>
<tr>
<td>
<p><code class="highlighter-rouge"><h3></h3></code></p>
</td>
<td><span class="h3">h3. Bootstrap heading</span></td>
</tr>
<tr>
<td>
<p><code class="highlighter-rouge"><h4></h4></code></p>
</td>
<td><span class="h4">h4. Bootstrap heading</span></td>
</tr>
<tr>
<td>
<p><code class="highlighter-rouge"><h5></h5></code></p>
</td>
<td><span class="h5">h5. Bootstrap heading</span></td>
</tr>
<tr>
<td>
<p><code class="highlighter-rouge"><h6></h6></code></p>
</td>
<td><span class="h6">h6. Bootstrap heading</span></td>
</tr>
</tbody>
</table>
<h2 id="lists">Lists</h2>
<p>All lists—<code class="highlighter-rouge"><ul></code>, <code class="highlighter-rouge"><ol></code>, and <code class="highlighter-rouge"><dl></code>—have their <code class="highlighter-rouge">margin-top</code> removed and a <code class="highlighter-rouge">margin-bottom: 1rem</code>. Nested lists have no <code class="highlighter-rouge">margin-bottom</code>.</p>
<div class="bd-example">
<ul>
<li>Lorem ipsum dolor sit amet</li>
<li>Consectetur adipiscing elit</li>
<li>Integer molestie lorem at massa</li>
<li>Facilisis in pretium nisl aliquet</li>
<li>Nulla volutpat aliquam velit
<ul>
<li>Phasellus iaculis neque</li>
<li>Purus sodales ultricies</li>
<li>Vestibulum laoreet porttitor sem</li>
<li>Ac tristique libero volutpat at</li>
</ul>
</li>
<li>Faucibus porta lacus fringilla vel</li>
<li>Aenean sit amet erat nunc</li>
<li>Eget porttitor lorem</li>
</ul>
<ol>
<li>Lorem ipsum dolor sit amet</li>
<li>Consectetur adipiscing elit</li>
<li>Integer molestie lorem at massa</li>
<li>Facilisis in pretium nisl aliquet</li>
<li>Nulla volutpat aliquam velit</li>
<li>Faucibus porta lacus fringilla vel</li>
<li>Aenean sit amet erat nunc</li>
<li>Eget porttitor lorem</li>
</ol>
</div>
<p>For simpler styling, clear hierarchy, and better spacing, description lists have updated <code class="highlighter-rouge">margin</code>s. <code class="highlighter-rouge"><dd></code>s reset <code class="highlighter-rouge">margin-left</code> to <code class="highlighter-rouge">0</code> and add <code class="highlighter-rouge">margin-bottom: .5rem</code>. <code class="highlighter-rouge"><dt></code>s are <strong>bolded</strong>.</p>
<div class="bd-example">
<dl>
<dt>Description lists</dt>
<dd>A description list is perfect for defining terms.</dd>
<dt>Euismod</dt>
<dd>Vestibulum id ligula porta felis euismod semper eget lacinia odio sem.</dd>
<dd>Donec id elit non mi porta gravida at eget metus.</dd>
<dt>Malesuada porta</dt>
<dd>Etiam porta sem malesuada magna mollis euismod.</dd>
</dl>
</div>
<h2 id="preformatted-text">Preformatted text</h2>
<p>The <code class="highlighter-rouge"><pre></code> element is reset to remove its <code class="highlighter-rouge">margin-top</code> and use <code class="highlighter-rouge">rem</code> units for its <code class="highlighter-rouge">margin-bottom</code>.</p>
<div class="bd-example">
<pre>
.example-element {
margin-bottom: 1rem;
}
</pre>
</div>
<h2 id="tables">Tables</h2>
<p>Tables are slightly adjusted to style <code class="highlighter-rouge"><caption></code>s, collapse borders, and ensure consistent <code class="highlighter-rouge">text-align</code> throughout. Additional changes for borders, padding, and more come with <a href="/docs/4.4/content/tables/">the <code class="highlighter-rouge">.table</code> class</a>.</p>
<div class="bd-example">
<table>
<caption>
This is an example table, and this is its caption to describe the contents.
</caption>
<thead>
<tr>
<th>Table heading</th>
<th>Table heading</th>
<th>Table heading</th>
<th>Table heading</th>
</tr>
</thead>
<tbody>
<tr>
<td>Table cell</td>
<td>Table cell</td>
<td>Table cell</td>
<td>Table cell</td>
</tr>
<tr>
<td>Table cell</td>
<td>Table cell</td>
<td>Table cell</td>
<td>Table cell</td>
</tr>
<tr>
<td>Table cell</td>
<td>Table cell</td>
<td>Table cell</td>
<td>Table cell</td>
</tr>
</tbody>
</table>
</div>
<h2 id="forms">Forms</h2>
<p>Various form elements have been rebooted for simpler base styles. Here are some of the most notable changes:</p>
<ul>
<li><code class="highlighter-rouge"><fieldset></code>s have no borders, padding, or margin so they can be easily used as wrappers for individual inputs or groups of inputs.</li>
<li><code class="highlighter-rouge"><legend></code>s, like fieldsets, have also been restyled to be displayed as a heading of sorts.</li>
<li><code class="highlighter-rouge"><label></code>s are set to <code class="highlighter-rouge">display: inline-block</code> to allow <code class="highlighter-rouge">margin</code> to be applied.</li>
<li><code class="highlighter-rouge"><input></code>s, <code class="highlighter-rouge"><select></code>s, <code class="highlighter-rouge"><textarea></code>s, and <code class="highlighter-rouge"><button></code>s are mostly addressed by Normalize, but Reboot removes their <code class="highlighter-rouge">margin</code> and sets <code class="highlighter-rouge">line-height: inherit</code>, too.</li>
<li><code class="highlighter-rouge"><textarea></code>s are modified to only be resizable vertically as horizontal resizing often “breaks” page layout.</li>
<li><code class="highlighter-rouge"><button></code>s and <code class="highlighter-rouge"><input></code> button elements have <code class="highlighter-rouge">cursor: pointer</code> when <code class="highlighter-rouge">:not(:disabled)</code>.</li>
</ul>
<p>These changes, and more, are demonstrated below.</p>
<form class="bd-example">
<fieldset>
<legend>Example legend</legend>
<p>
<label for="input">Example input</label>
<input type="text" id="input" placeholder="Example input" />
</p>
<p>
<label for="select">Example select</label>
<select id="select">
<option value="">Choose...</option>
<optgroup label="Option group 1">
<option value="">Option 1</option>
<option value="">Option 2</option>
<option value="">Option 3</option>
</optgroup>
<optgroup label="Option group 2">
<option value="">Option 4</option>
<option value="">Option 5</option>
<option value="">Option 6</option>
</optgroup>
</select>
</p>
<p>
<label>
<input type="checkbox" value="" />
Check this checkbox
</label>
</p>
<p>
<label>
<input type="radio" name="optionsRadios" id="optionsRadios1" value="option1" checked="" />
Option one is this and that
</label>
<label>
<input type="radio" name="optionsRadios" id="optionsRadios2" value="option2" />
Option two is something else that's also super long to demonstrate the wrapping of these fancy form controls.
</label>
<label>
<input type="radio" name="optionsRadios" id="optionsRadios3" value="option3" disabled="" />
Option three is disabled
</label>
</p>
<p>
<label for="textarea">Example textarea</label>
<textarea id="textarea" rows="3"></textarea>
</p>
<p>
<label for="date">Example date</label>
<input type="date" id="date" />
</p>
<p>
<label for="time">Example time</label>
<input type="time" id="time" />
</p>
<p>
<label for="output">Example output</label>
<output name="result" id="output">100</output>
</p>
<p>
<button type="submit">Button submit</button>
<input type="submit" value="Input submit button" />
<input type="reset" value="Input reset button" />
<input type="button" value="Input button" />
</p>
<p>
<button type="submit" disabled="">Button submit</button>
<input type="submit" value="Input submit button" disabled="" />
<input type="reset" value="Input reset button" disabled="" />
<input type="button" value="Input button" disabled="" />
</p>
</fieldset>
</form>
<h2 id="misc-elements">Misc elements</h2>
<h3 id="address">Address</h3>
<p>The <code class="highlighter-rouge"><address></code> element is updated to reset the browser default <code class="highlighter-rouge">font-style</code> from <code class="highlighter-rouge">italic</code> to <code class="highlighter-rouge">normal</code>. <code class="highlighter-rouge">line-height</code> is also now inherited, and <code class="highlighter-rouge">margin-bottom: 1rem</code> has been added. <code class="highlighter-rouge"><address></code>s are for presenting contact information for the nearest ancestor (or an entire body of work). Preserve formatting by ending lines with <code class="highlighter-rouge"><br></code>.</p>
<div class="bd-example">
<address>
<strong>Twitter, Inc.</strong><br />
1355 Market St, Suite 900<br />
San Francisco, CA 94103<br />
<abbr title="Phone">P:</abbr> (123) 456-7890
</address>
<address>
<strong>Full Name</strong><br />
<a href="mailto:first.last@example.com">first.last@example.com</a>
</address>
</div>
<h3 id="blockquote">Blockquote</h3>
<p>The default <code class="highlighter-rouge">margin</code> on blockquotes is <code class="highlighter-rouge">1em 40px</code>, so we reset that to <code class="highlighter-rouge">0 0 1rem</code> for something more consistent with other elements.</p>
<div class="bd-example">
<blockquote class="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>
</div>
<h3 id="inline-elements">Inline elements</h3>
<p>The <code class="highlighter-rouge"><abbr></code> element receives basic styling to make it stand out amongst paragraph text.</p>
<div class="bd-example">
Nulla <abbr title="attribute">attr</abbr> vitae elit libero, a pharetra augue.
</div>
<h3 id="summary">Summary</h3>
<p>The default <code class="highlighter-rouge">cursor</code> on summary is <code class="highlighter-rouge">text</code>, so we reset that to <code class="highlighter-rouge">pointer</code> to convey that the element can be interacted with by clicking on it.</p>
<div class="bd-example">
<details>
<summary>Some details</summary>
<p>More info about the details.</p>
</details>
<details open="">
<summary>Even more details</summary>
<p>Here are even more details about the details.</p>
</details>
</div>
<h2 id="html5-hidden-attribute">HTML5 <code class="highlighter-rouge">[hidden]</code> attribute</h2>
<p>HTML5 adds <a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/hidden">a new global attribute named <code class="highlighter-rouge">[hidden]</code></a>, which is styled as <code class="highlighter-rouge">display: none</code> by default. Borrowing an idea from <a href="https://purecss.io/">PureCSS</a>, we improve upon this default by making <code class="highlighter-rouge">[hidden] { display: none !important; }</code> to help prevent its <code class="highlighter-rouge">display</code> from getting accidentally overridden. While <code class="highlighter-rouge">[hidden]</code> isn’t natively supported by IE10, the explicit declaration in our CSS gets around that problem.</p>
<figure class="highlight"><pre><code class="language-html" data-lang="html"><span class="nt"><input</span> <span class="na">type=</span><span class="s">"text"</span> <span class="na">hidden</span><span class="nt">></span></code></pre></figure>
<div class="bd-callout bd-callout-warning">
<h5 id="jquery-incompatibility">jQuery incompatibility</h5>
<p><code class="highlighter-rouge">[hidden]</code> is not compatible with jQuery’s <code class="highlighter-rouge">$(...).hide()</code> and <code class="highlighter-rouge">$(...).show()</code> methods. Therefore, we don’t currently especially endorse <code class="highlighter-rouge">[hidden]</code> over other techniques for managing the <code class="highlighter-rouge">display</code> of elements.</p>
</div>
<p>To merely toggle the visibility of an element, meaning its <code class="highlighter-rouge">display</code> is not modified and the element can still affect the flow of the document, use <a href="/docs/4.4/utilities/visibility/">the <code class="highlighter-rouge">.invisible</code> class</a> instead.</p>
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