I found it really interesting that the way the images on this site load is fading from fuzzy to clear, how exactly does that work?

What I can say for sure is that this image loading mode uses at least lazyload, as well as thumbnails and original images, when visiting the web page all images are downloaded as thumbnails, and then the original image is downloaded via lazyload, but that doesn’t explain the process of the image going from fuzzy to clear, it’s not a simple switch between the two images