add_filter('script_loader_tag', function($tag, $handle){ $defer_handles = [ 'dcportal', // bookings.d14e.io (rename if your handle differs) 'contact-form-7', 'swiper', 'slick', 'us-core', // Zephyr core JS (safe to defer in most cases) 'us-plugins', // Zephyr plugins bundle (often safe) ]; // Never defer these: $deny = ['jquery', 'jquery-core', 'jquery-migrate']; if ( in_array($handle, $deny, true) ) return $tag; if ( in_array($handle, $defer_handles, true) ) { return str_replace(' src=', ' defer src=', $tag); } return $tag; }, 10, 2);