If you need it for your development environment you can enable `settings.local.php` in your `settings.php` if (file_exists($app_root . '/' . $site_path . '/settings.local.php')) { include $app_root . '/' . $site_path . '/settings.local.php'; } and than make sure ONLY in your local `settings.local.php` (not on your live enviroment) the following settings are used $config['system.performance']['css']['preprocess'] = FALSE; $config['system.performance']['js']['preprocess'] = FALSE;