Context: Even though Chromium has native support for AVIF, a very nice image format, Microsoft goes out of their way to remove it from Edge, which is a chromium fork. Jpeg XL (JXL) (not to be confused with Jpeg (JPG) or Jpeg 2000 (jpg2k) ) is another nice image format, which, IIRC, is only supported in Firefox.
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Thanks for the info! I was already suspecting that this could be done without JS, just didn’t know how.