rocket-lazyload-mobile.php

<?php
defined( 'ABSPATH' ) or die( 'Cheatin&#8217; uh?' );
/**
 * Plugin Name: WP Rocket | LazyLoad Mobile
 * Description: Enable LazyLoad only for mobile
 * Author:      WP Rocket Support Team
 * Author URI:  http://wp-rocket.me/
 * License:     GNU General Public License v3 or later
 * License URI: http://www.gnu.org/licenses/gpl-3.0.html
 */

add_filter( 'wp', 'rocket_enable_lazyload_only_on_mobile' );
function rocket_enable_lazyload_only_on_mobile() {
	if( class_exists( 'Rocket_Mobile_Detect' ) && get_rocket_option( 'do_caching_mobile_files', false ) ) {
		$detect = new Rocket_Mobile_Detect();
			// Images
			add_filter( 'do_rocket_lazyload', '__return_false' );
			
			// Iframes
			add_filter( 'do_rocket_lazyload_iframes', '__return_false' );

		if ( $detect->isMobile() && ! $detect->isTablet() ) {
			// Images
			add_filter( 'do_rocket_lazyload', '__return_true' );
			
			// Iframes
			add_filter( 'do_rocket_lazyload_iframes', '__return_true' );
		}
	}
}