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Accessibility &middot; Bootstrap
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<li class="toc-entry toc-h3"><a href="#structural-markup">Structural markup</a></li>
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<h1 class="bd-title" id="content">Accessibility</h1>
<p class="bd-lead">A brief overview of Bootstrap's features and limitations for the creation of accessible content.</p>
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<p>Bootstrap provides an easy-to-use framework of ready-made styles, layout tools, and interactive components, allowing developers to create websites and applications that are visually appealing, functionally rich, and accessible out of the box.</p>
<h2 id="overview-and-limitations">Overview and Limitations</h2>
<p>The overall accessibility of any project built with Bootstrap depends in large part on the authors markup, additional styling, and scripting theyve included. However, provided that these have been implemented correctly, it should be perfectly possible to create websites and applications with Bootstrap that fulfill <a href="https://www.w3.org/TR/WCAG20/"><abbr title="Web Content Accessibility Guidelines">WCAG</abbr> 2.0</a> (A/AA/AAA), <a href="https://www.section508.gov/">Section 508</a> and similar accessibility standards and requirements.</p>
<h3 id="structural-markup">Structural markup</h3>
<p>Bootstraps styling and layout can be applied to a wide range of markup structures. This documentation aims to provide developers with best practice examples to demonstrate the use of Bootstrap itself and illustrate appropriate semantic markup, including ways in which potential accessibility concerns can be addressed.</p>
<h3 id="interactive-components">Interactive components</h3>
<p>Bootstraps interactive components—such as modal dialogs, dropdown menus and custom tooltips—are designed to work for touch, mouse and keyboard users. Through the use of relevant <a href="https://www.w3.org/WAI/intro/aria"><abbr title="Web Accessibility Initiative">WAI</abbr>-<abbr title="Accessible Rich Internet Applications">ARIA</abbr></a> roles and attributes, these components should also be understandable and operable using assistive technologies (such as screen readers).</p>
<p>Because Bootstraps components are purposely designed to be fairly generic, authors may need to include further <abbr title="Accessible Rich Internet Applications">ARIA</abbr> roles and attributes, as well as JavaScript behavior, to more accurately convey the precise nature and functionality of their component. This is usually noted in the documentation.</p>
<h3 id="color-contrast">Color contrast</h3>
<p>Most colors that currently make up Bootstraps default palette—used throughout the framework for things such as button variations, alert variations, form validation indicators—lead to <em>insufficient</em> color contrast (below the recommended <a href="https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html">WCAG 2.0 color contrast ratio of 4.5:1</a>) when used against a light background. Authors will need to manually modify/extend these default colors to ensure adequate color contrast ratios.</p>
<h3 id="visually-hidden-content">Visually hidden content</h3>
<p>Content which should be visually hidden, but remain accessible to assistive technologies such as screen readers, can be styled using the <code class="highlighter-rouge">.sr-only</code> class. This can be useful in situations where additional visual information or cues (such as meaning denoted through the use of color) need to also be conveyed to non-visual users.</p>
<figure class="highlight"><pre><code class="language-html" data-lang="html"><span class="nt">&lt;p</span> <span class="na">class=</span><span class="s">"text-danger"</span><span class="nt">&gt;</span>
<span class="nt">&lt;span</span> <span class="na">class=</span><span class="s">"sr-only"</span><span class="nt">&gt;</span>Danger: <span class="nt">&lt;/span&gt;</span>
This action is not reversible
<span class="nt">&lt;/p&gt;</span></code></pre></figure>
<p>For visually hidden interactive controls, such as traditional “skip” links, <code class="highlighter-rouge">.sr-only</code> can be combined with the <code class="highlighter-rouge">.sr-only-focusable</code> class. This will ensure that the control becomes visible once focused (for sighted keyboard users).</p>
<figure class="highlight"><pre><code class="language-html" data-lang="html"><span class="nt">&lt;a</span> <span class="na">class=</span><span class="s">"sr-only sr-only-focusable"</span> <span class="na">href=</span><span class="s">"#content"</span><span class="nt">&gt;</span>Skip to main content<span class="nt">&lt;/a&gt;</span></code></pre></figure>
<h2 id="additional-resources">Additional resources</h2>
<ul>
<li><a href="https://www.w3.org/TR/WCAG20/">Web Content Accessibility Guidelines (WCAG) 2.0</a></li>
<li><a href="http://a11yproject.com/">The A11Y Project</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/Accessibility">MDN accessibility documentation</a></li>
<li><a href="https://tenon.io/">Tenon.io Accessibility Checker</a></li>
<li><a href="https://www.paciellogroup.com/resources/contrastanalyser/">Colour Contrast Analyser (CCA)</a></li>
<li><a href="https://github.com/squizlabs/HTML_CodeSniffer">“HTML Codesniffer” bookmarklet for identifying accessibility issues</a></li>
</ul>
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