

All you have to do is add a small traditional JPEG image at the start of the file. It doesn’t have to be high resolution or more than a couple of kb. The new format decoder would know this, and skip the traditional jpeg “header”, rendering the newer file format embedded in the image.








If you’re really saving 20% in file size with XL, adding back a very compressed preview image that takes up one or two percent isn’t going to cost you much.