is_404() WordPress Function

function is_404() {
	global $wp_query;

	if ( ! isset( $wp_query ) ) {
		_doing_it_wrong( __FUNCTION__, __( 'Conditional query tags do not work before the query is run. Before then, they always return false.' ), '3.1.0' );
		return false;
	}

	return $wp_query->is_404();
}
Uses	Description
wp-includes/l10n.php:__()	Retrieve the translation of $text.
wp-includes/class-wp-query.php:WP_Query::is_404()	Is the query a 404 (returns no results)?
wp-includes/functions.php:_doing_it_wrong()	Mark something as being incorrectly called.
Used By	Description
wp-includes/embed.php:print_embed_comments_button()	Prints the necessary markup for the embed comments button.
wp-includes/embed.php:print_embed_sharing_button()	Prints the necessary markup for the embed sharing button.
wp-includes/embed.php:print_embed_sharing_dialog()	Prints the necessary markup for the embed sharing dialog.
wp-includes/general-template.php:wp_get_document_title()	Returns document title for the current page.
wp-includes/general-template.php:wp_title()	Display or retrieve page title for all areas of blog.
wp-includes/class-wp.php:WP::handle_404()	Set the Headers for 404, if nothing is found for requested URL.
wp-includes/query.php:wp_old_slug_redirect()	Redirect old slugs to the correct permalink.
wp-includes/post-template.php:get_body_class()	Retrieves an array of the class names for the body element.
wp-includes/canonical.php:redirect_canonical()	Redirects incoming links to the proper URL based on the site url.
wp-includes/canonical.php:wp_redirect_admin_locations()	Redirects a variety of shorthand URLs to the admin.
wp-includes/ms-functions.php:maybe_redirect_404()	Corrects 404 redirects when NOBLOGREDIRECT is defined.