Enable Theme Debug in Drupal 9

services.yml Navigate to  \sites\default create a the file sites/default/services.yml from sites/default/ set the parameters as follows: parameters: twig.config: debug: true auto_reload: true cache: false settings.local.php  Navigate to / sites/ Make a copy of   example.settings.local.php   and rename it to   settings.local.php Locate the following lines and uncomment # $settings['cache']['bins']['render'] = 'cache.backend.null'; # $settings['cache']['bins']['page'] = 'cache.backend.null'; # $settings['cache']['bins']['dynamic_page_cache'] = 'cache.backend.null'; settings.php Navigate to  sites\default Open  settings.php  and search for ' local.php ' You should then find the following code block if (file_exists($app_root . '/' . $site_path . '/settings.local.php')) { include $app_root . '/' . $site_path . '/settings.local.php'; }