WordPress introduced “Lazy Loading*” of images a little more than half a year ago, in version 5.5. Previously, one had to use a plugin to get that feature and in fact, it was included in many caching and optimization plugins, as well as WordPress’s own “Jetpack” multi-functionality plugin.
When WordPress 5.5 was released I asked in the Jetpack support forum whether the Jetpack “Lazy Load” feature can be disabled now (wouldn’t want two features like that to interfere because who knows, it might break image loading altogether, or whatever else). That was confirmed, and so I went ahead and disabled Jetpack’s “Lazy Load” feature, in favor of the WordPress 5.5 built in functionality.
I didn’t bother to test it until recently, when I wrote about photo presentation online — to then find out that, while the WordPress Lazy Load works fine on desktop browsers, it doesn’t “lazy load” any images on mobile devices! I tested this with Safari and Firefox on an iPhone and the bigger galleries like my Color and Black & White portfolios were just awfully slow.
Since I have both a caching plugin with a Lazy Load option and Jetpack installed, I tried both of these Lazy Load features instead, and both of them work on mobile, as expected. In the end I went with Jetpack’s Lazy Load again, which seemed to look and work better.
I’m scratching my head why the native WordPress lazy loading of images isn’t working on mobile for me. I tried this both on my self-hosted photography site and this personal blog here, using galleries. The way it looks, it’s not working on either, so it can’t be my theme or some plugin interference.
In any case, if you rely on Lazy Load, then you might want to double check on mobile. For testing it might be useful to disable the WiFi on your phone and use cellular data instead (depending on the speed of your internet connection and WiFi of course — if it’s fast, you might not be able to see whether the lazy loading works or not).
Let me know what you find. Is WordPress 5.5+ Lazy Load working correctly on mobile for you?
*) “Lazy Loading” means that web browsers (that support the feature, and by now most if not all of them do) are instructed to only load those images that are actually visible. It’s a very simple method to speed up website loading times. If you have an article or gallery with 50 images in them, only the first few will load, and then the browser will “catch up” and load the remaining images later, as you scroll down.