Follow the link below for a details article on how to Async your site's JavaScript.
https://kinsta.com/blog/google-pagespeed-insights/
/*function to add async to all scripts*/ function js_async_attr($tag){ # Add async to all remaining scripts return str_replace( ' src', ' async="async" src', $tag ); } add_filter( 'script_loader_tag', 'js_async_attr', 10 );