It turns out, lazy loading does work with responsive images in Firefox 75: for this to work, you currently have to put the
loading attribute before
srcset in the attribute list of an
img tag. This is a bug, and will be fixed in a future release.
So, I changed my markup accordingly – both on this site and the photo journal.
As for Firefox’ implementation itself: I find it currently too lazy. A new image is only downloaded when it’s already inside the viewport. This is going to result in visitors (unnecessarily) having to wait for an image download, especially when the image is larger and/or their internet connection is not the fastest.
Chrome’s implementation on the other hand is more appropriate in my opinion: it starts downloading images marked with
loading=lazy well in advance – a few full “screens” before they are actually reached via scrolling.
Anyhow: happy this got implemented in Firefox now, too, despite its implementation needing a bit more refinement in my opinion.