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

global $wp_query;
$wp_query->is_preview();

Changelog

Since 3.1.0 Introduced.

Code of WP_Query::is_preview() WP 5.7.2

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