One SEO professional asked John Mueller during a hangout about Lazy loading CSS. They explained that they had implemented a CDN for Lazy loading JS and CSS.
They found that this had increased their Core Web Vitals by at least 50 percent.
They just wanted to make sure that making such a change wouldn’t impact them negatively in any way.
John replied that it’s just fine to do things exactly like this, especially for CSS. It’s important, however, to consider how CSS does load because this could affect whether or not a page looks like it is mobile friendly to Google.
That’s something important to look out for.
Otherwise, John explains that it’s perfectly acceptable to use Lazy loading on CSS.
This happens at approximately the 32:22 mark in the video.
John Mueller Hangout Transcript
SEO Professional 6 32:22
It does. Yes. Thank you for answering that. I only want to add first of all, yeah, the h…so the links out there. So we’re good with that. And what we’re trying to address here is the Page Speed, which we’re using the CDN which does this part of the Lazy loading, let’s say JS and CSS. So yes, we’re trying to increase the speed, this did increase the web vitals as well, by like, a lot more than 50%. So I don’t know if such a big change will affect us in any way, in a bad way. Is this considered, I mean, lazy loading CSS, a bad practice? Or is there anything on that?