When a PNG copy helps
Use JFIF to PNG for a slide, editor, or form that refuses the original format. Changing a filename from .jfif to .png does not create a PNG; this converter decodes the picture and writes a new image.
After downloading, open the copy in your destination app. Check its orientation, colors, and dimensions before replacing the source. See how file extensions differ from image data if a JPG copy might be enough.