select2/docs/_includes/options-new/selections/multiple.html

<section>
  <h2 id="multiple">
    Can I allow users to make multiple selections?
  </h2>

  <p>
    Yes, Select2 supports making multiple selections through the use of the <code>multiple</code> option that can be passed in when initializing Select2.
  </p>

  <h3>
    Can the <code>multiple</code> attribute be used on my <code>&lt;select&gt;</code> element?
  </h3>

  <p>
    Yes, Select2 will automatically map the value of the <code>multiple</code> attribute to the <code>multiple</code> option during initialization.
  </p>
</section>