Enable Twig debug mode in drupal 9+ (Optional) Enable render caching debugging

In your sites/development.services.yml, add the following twig.config configuration nested under the parameters key:

# Local development services.
#
# To activate this feature, follow the instructions at the top of the
# 'example.settings.local.php' file.
parameters:
  http.response.debug_cacheability_headers: true
  twig.config:
    debug: true
    auto_reload: true
    cache: false
services:
  cache.backend.null:
    class: Drupal\Core\Cache\NullBackendFactory

(Optional) Enable render caching debugging

To enable render caching debugging, update renderer.config and set its debug parameter value to true in your site's services.yml or development.services.yml.

parameters:
  http.response.debug_cacheability_headers: true
  twig.config:
    debug: true
    auto_reload: true
    cache: false
  renderer.config:
    required_cache_contexts: ['languages:language_interface', 'theme', 'user.permissions']
    auto_placeholder_conditions:
      max-age: 0
      contexts: ['session', 'user']
      tags: []
    debug: true