I am trying to remove all unnecessary/unused stylesheets for anonymous visitors to get better performance and a clean <head> section. This works fine by listing them inside mytheme.info.yml:

  - path/to/stylesheet.css
  - path/to/another/stylesheet.css
  - core/modules/system/css/components/hidden.module.css

However, the third entry in this example breaks the styling of the toolbar - which is only visible to the admin. Is it possible to programatically tell Drupal which stylesheets to remove only for anonymous visitors? I appreciate your help!

2 Answers 2


Having tried to do this myself before, this is probably not a route you want to go down. This approach becomes harder to maintain as you install more modules (different modules can inject CSS on different paths), and often can turn into a maintenance nightmare.

Drupal can aggregate CSS files out of the box; this is often all you need to improve performance dramatically.

To turn on the basic aggregation, you can check Aggregate CSS files at /admin/config/development/performance.

To do something more complicated, try using the Advagg module. Configuring this module can be complex but it allows you to do more specific aggregation, CSS minification, and so on.

  • Yes, I agree that this solution is definitely better for maintainability. I will take a look at the Advagg module as well. Thanks for your help! Commented Jul 16, 2020 at 11:06

you can use hook bellow (check for the right path)

function MYMODULE_page_attachments_alter(array &$attachments) {
  if(\Drupal::currentUser()->isAnonymous()) {
  • 1
    That seems to be the way to go, although I think it has to be $attachments['#attached']['library'][0] in order to remove all the system css stuff. Thanks! Commented Jul 14, 2020 at 17:57
  • 1
    You can only remove libraries but not a single CSS file like that.
    – leymannx
    Commented Jul 14, 2020 at 22:06
  • 1
    You can only remove libraries added by other hook_page_attachments or hook_page_attachments_alter implementations.
    – 4uk4
    Commented Jul 15, 2020 at 6:59
  • 1
    @4k4 – ... or added from a theme's info file.
    – leymannx
    Commented Jul 15, 2020 at 7:41
  • 1
    $attachments['#attached'['library'['core/modules/system/css/components/hidden.module.cs'] contains a syntax error.
    – apaderno
    Commented Jul 15, 2020 at 8:44

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