Support » Fixing WordPress » WordPress 4.8 editor “Failed to load content css”

  • Resolved wp_kc


    After updating to WordPress 4.8, editing a post causes a floating error message to appear at the top of the editor saying that it could not load the theme’s editor-style sheet. The message says, “Failed to load content css:”


    • WordPress 4.8 on Ubuntu w/ Apache2
    • Twentyseventeen theme installed
    • Using child theme of Twentyseventeen.
    • The file mentioned above does exist.
    • The child theme was working fine and did not produce this error before the update of WordPress and the Twentyseventeen theme.
    • The strangest part is that I can confirm that the css file in question is being downloaded by the browser and is having an effect on the editor. The actual URL being generated by WP is:
    • This is the editor style code in my child theme’s functions.php file:
      function child_theme_setup() {
              get_stylesheet_directory_uri() . '/assets/css/editor-style.css',
      add_action('after_setup_theme', 'child_theme_setup', 99);
Viewing 3 replies - 31 through 33 (of 33 total)
  • Yogendra Sharma


    In my case, when i updated to WP 4.8, the code editor shows the error Failed to load content css:
    In the previous posts, guys facing only with particular files like style.css, editor.css etc. but in my case, it shows the complete ‘themes’ directory.
    Even the whole site is working fine but error comes though.



    And what is very strange is that the special font (Allura or other) are ok on my frontend webside !
    So the problem is just the error message, no ?

    Moderator Marius L. J.


    This thread is quite literally just us repeating things over and over, and is taking up time that could be better used elsewhere.

    As such, I will close the thread, to save everyone form posting “me too” related posts, but we’ve written a more detailed explanation of the problem in our general troubleshooting posts, I’ll be quoting it here as well, so that anyone who stumbles upon this post are guaranteed to see it:

    Failed to load content css

    This issue keeps popping up for users after the 4.8 update, so here’s a more in-depth process of what is happening.

    The error means that the editor window was unable to load one or more resources, generally added using the editor_styles function, this is primarily added by your theme, but can also be implemented by plugins (if you would like to identify the exact cause of it, please follow the regular troubleshooting steps outlined in the first post of this thread).

    This issue can have many root causes, I’ll run through some of them, so you know what you are looking for, or what to inform your theme developer about:

    • The style file does not exist at all
    • The style file uses one or more @import() calls to include files, but the path is wrong
    • Your site is using SSL (your URL starts with https://), but the resources being loaded are trying to use un-encrypted http:// links
    • The URL being included is an external one, and is incorrect. So far primarily seen with Google Fonts, where a %2C is added to the end of the link (this is considered a comma, and the link is invalid from Googles point of view if it ends like this)

    All of these situations, and probably some other scenarios we’ve not outlined, cause the warning to show up. What is important to take note of here is that this is just that, a warning, it will not affect the performance of your website, it just means the text editor window won’t preview what it will look like as accurately as it could.

    This is not a bug in WordPress 4.8, but rather a warning introduced to help you get the best possible editor experience, but unfortunately it is up to the theme and plugin developers to implement the features correctly.

Viewing 3 replies - 31 through 33 (of 33 total)
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