required

• Description
• Syntax
• Examples
• Links

The required pseudo-class for CSS applies when an element is required.

selector:required
{
    property: value;
}

• optional

• active
• any-link
• autofill
• blank
• checked
• default
• defined
• dir
• disabled
• empty
• enabled
• first-child
• first-of-type
• focus
• focus-visible
• focus-within
• fullscreen
• has
• hover
• in-range
• indeterminate
• invalid
• is
• lang
• last-child
• last-of-type
• link
• local-link
• modal
• not
• nth-child
• nth-col
• nth-last-child
• nth-last-col
• nth-last-of-type
• nth-of-type
• only-child
• only-of-type
• optional
• out-of-range
• picture-in-picture
• placeholder-shown
• popover-open
• read-only
• read-write
• root
• scope
• target
• valid
• visited
• where

• World Wide Web Consortium (W3C)