How to render a hidden input field
_input elements of type hidden let web developers include data that cannot be seen or modified by users when a form is submitted. For example, the ID of the content that is currently being ordered or edited, or a unique security token. Hidden inputs are completely invisible in the rendered page, and there is no way to make it visible in the page's content.
All other valid parameters for an input field are valid
<_input type="hidden" name="token" value="123231321" />
While the value isn't displayed to the user in the page's content, it is visible—and can be edited—using any browser's developer tools or "View Source" functionality. If you want to create a secure field, then use _input type="secure".