Why do I get the message "Eliminate render-blocking resources" when using ShortPixel?

Have you ever used GTmetrix or PageSpeed Insights, and you got the message "Eliminate render-blocking resources" with some URLs pointing to cdn.shortpixel.ai?

In short, this message is related to your theme or plugins, and ShortPixel cannot fix this.

As GTmetrix explains, render-blocking resources are scripts (JavaScript files) or stylesheets (CSS files) that block or delay the browser from rendering page content to the screen. The fact that they are hosted on our CDN doesn't mean that the issue is on ShortPixel's side; it only means that by installing ShortPixel Adaptive Images (SPAI) you are simply serving those files from our CDN, which should be actually faster.

GTmetrix has good documentation about how to solve this, but take into account that most of the times the resources that are marked as render-blocking have to be render-blocking. That's especially true in most of CSS files, as you wouldn't want to serve a page with no style to your clients. It is also true if you see ShortPixe'ls own JavaScript file (ai.min.js). Deferring SPAI's resources will probably make the plugin stop working and stop showing your images. To learn more about why SPAI is not working correctly, have a look at this article.

You can contact your theme or plugin providers in order to know more about specific resources. For instance, on the previous screenshot we can see that the CSS file is loaded by the plugin "Structured Content (JSON-LD) #wpsc", so they are who could provide more insights about the topic.