pagespeed insights – defer css in autoptimize file

Morning dcottreau;
I assume you already have “inline & defer” (and potentially the “Autoptimze criticalcss.com power-up”) active already?

When you’re using “inline & defer” the critical CSS is inlined and the full CSS is technically not deferred but “preloaded” meaning it is loaded without it being render-blocking (which is a separate GPSI recommendation). AO uses Filamentgroup’s loadCSS for this purpose.

The advantage of using “preload” is that the page below the fold is styled as soon as possible without the CSS being render blocking. If it would be deferred (as AO used to do a couple of versions ago) that CSS would be loaded later and the chance was bigger that the user scrolled down to a part of the page that was not styled yet.

Given the fact that preloading the full CSS does not block rendering, there is little advantage to be found in deferring it instead and the disadvantage might be significant.

tldr; that warning is a false positive, just ignore it ??

Hope this clarifies,
frank

Ok thanks. I am using inline and defer right now. I configured that using the method from wpfaster. This is the only remaining item listed under opportunities so if we can’t “fix” this, I guess we can’t really get the score much higher?

without seeing the site itself it’s hard to say for sure if the performance can be further improved (as there’s more to performance then what GPSI lists as opportunity) but based on the info you provided; yes, you can’t get the score much higher.

Sorry, I also forgot to mention I am not using the critical.css power-up. Given that the desktop speeds are at 100% and the mobile is at 76% – will adding this really help much more? As I said, there are no other opportunities on the mobile side listed.

well, depends; are your GPSI scores (which are not “speeds” really, but “just” an attempt at quantifying best practices being followed) similar for all your pages? because “inline & defer” injects the same critical CSS for all pages, which in most cases is OK for some pages, but not OK for others …