Support » Plugin: Jetpack Boost - Website Speed, Performance and Critical CSS » Failed to generate Critical CSS

  • Resolved born2excite


    I recently installed Jetpack Boost on my SiteGround staging site.

    Jetpack Boost has never been able to get the site score and never been able to generate Critical CSS. Please see the error message below:

    Whoops, something went wrong
    Couldn't get the site score Retry
    Timed out while waiting for metrics
    Failed to generate Critical CSS:
    i.existsSync is not a function
    Try again, or contact Jetpack Boost support for assistance.

    For information, I’m using PHP 7.4.16

    Can you please consider the cause and fix for this problem?


Viewing 6 replies - 1 through 6 (of 6 total)
  • Plugin Author Nauris (a11n)


    Hi there,
    Is your staging site online? What’s the URL?

    Can you post a list of currently active plugins?

    Thread Starter born2excite


    Thanks for your help and quick reply, @pyronaur

    Yes, the staging site is online and the URL is:

    Active Plugins

    Admin Menu Editor
    Akismet Anti-Spam
    Code Snippets
    Disable Lazy Load
    Easy WP SMTP
    Head, Footer and Post Injections
    Jetpack Boost
    Jetpack by
    Media Library Folders for WordPress
    Porto Theme – Functionality
    Printful Integration for WooCommerce
    SG Optimizer
    WooCommerce Shipping & Tax
    WooCommerce Stripe Gateway
    Wordfence Security
    WP-Optimize - Clean, Compress, Cache
    WPBakery Page Builder
    YITH WooCommerce Ajax Search
    YITH WooCommerce Wishlist

    Thank you,



    Similar issue:
    Failed to generate Critical CSS:
    Failed to verify page at

    Try again, or contact Jetpack Boost support for assistance.

    Plugin Author Nauris (a11n)


    Hi, @paontheweb!
    Can you start a new thread? That seems to be a slightly different issue. When you post the thread – can you also include a list of your currently active plugins?

    Hello @born2excite,

    I am glad to help!

    To continue our troubleshooting, could you deactivate the Rocket Loader option from your Cloudflare, please?

    Then, clean the Cloudflare cache and wait some minutes before you retry the Jetpack Boost analysis again.

    If the issue with Jetpack Boost persists, please contact us back for further investigation.

    Let me know if you have any questions.

    My best regards,

    Thread Starter born2excite


    Hello Michelle @deathlynotes

    After updating Jetpack Boost to version 1.0.3, the plugin can now generate Critical CSS.

    However, calculating the site score still does not work. I’m not really concerned so I have no need to continue troubleshooting this issue.

    I didn’t deactivate the Rocket Loader option in Cloudflare because as stated above, Jetpack Boost is now able to generate the critical CSS. Which is all I was really interested in.

    Thanks for your help, I appreciate your time and effort.

Viewing 6 replies - 1 through 6 (of 6 total)
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