Hi @bixfrankonis,
To clarify why this is happening and why Critical CSS generator fails in your case, let’s dive into how Jetpack Boost’s Critical CSS generator feature, and critical CSS generators in general, operate—tailored to your situation.
Critical CSS generators are designed to enhance your site’s loading speed by identifying and prioritizing the CSS needed for the initial display of your pages—essentially, the styles that are critical for rendering the portion of your website that visitors see first, without scrolling. Jetpack Boost automates this process for your site, aiming to improve your site’s performance and the user experience.
Here’s where the conflict arises with your setup: Your blog utilizes a custom 404 page plugin that redirects any direct attempts to access the custom 404 page URL back to your blog’s main page. When Jetpack Boost’s Critical CSS generator tries to analyze your custom 404 page to extract the critical CSS, it can’t do so effectively because of this redirect. Instead of analyzing the actual content and layout of the 404 page, the generator is taken back to the main page. This behavior prevents the generator from determining what CSS is truly critical for the 404 page, potentially leading to the “failed to generate critical CSS” error you’re experiencing.
This issue is indicative of the sensitive nature of critical CSS generation processes: they require stable, direct access to each page they’re analyzing to accurately capture and prioritize the necessary styles. Any form of redirection or interruption during this process can disrupt the analysis, leading to incomplete or failed critical CSS generation attempts.
In the context of your blog and the use of Jetpack Boost, this means the interaction between the custom 404 page plugin’s redirection and the Critical CSS generator is at the heart of the problem. While this scenario is specific to your site’s configuration and the tools you’re using, it’s reflective of a broader principle in web performance optimization: ensuring that all components of a site, from plugins to performance tools like Jetpack Boost, are working harmoniously to achieve the best possible loading speeds and user experience.
I hope this explanation helps clarify why you’re encountering issues with generating critical CSS for your blog and sheds light on the intricacies of how critical CSS generators operate, especially in complex or unique site configurations like yours.
I hope this helps.