WordPress at a glance
function is not described

WP_Query::is_preview() public WP 3.1.0

Is the query for a post or page preview?

It's a method of the class: WP_Query{}

No Hooks.

Return

true/false. Whether the query is for a post or page preview.

Usage

$WP_Query = new WP_Query();
$WP_Query->is_preview();

Changelog

Since 3.1.0 Introduced.

Code of WP_Query::is_preview() WP 5.5.1

<?php
public function is_preview() {
	return (bool) $this->is_preview;
}