=&quot;val&quot; aria-required=&quot;true&quot;&gt;&lt;/md-checkbox&gt;
</code></pre>
<h2 id="ngreadonly">ngReadonly</h2>

<p>The boolean <code>readonly</code> attribute is only valid for native form controls such as <code>input</code> and
<code>textarea</code>. To properly indicate custom element directives such as <code>&lt;md-checkbox&gt;</code> or <code>&lt;custom-input&gt;</code>
as required, using ngAria with <a href="api/ng/directive/ngReadonly">ngReadonly</a> will also add
<code>aria-readonly</code>