HTML Global hidden Attribute

<p hidden>I'm hidden paragraph</p>

<p>I'm visible paragraph</p>

Meaning

The hidden attribute is a Boolean, or presence-based, attribute that does not require a value.

The element is not currently relevant and the user agent should not render it when this attribute is specified

This attribute was initially called irrelevant in earlier HTML5 drafts.

In XHTML5, you should use the value of hidden, as attributes must have values with XML syntax.

If elements styled display: flex; will be displayed despite the hidden attribute's presence.

<element hidden>

Value	Description
hidden	This is a boolean attribute, the presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.