Why your iPhone photos are HEIC
The iPhone camera saves photos as HEIC. HEIC is a compact, lossy photo format for the library on the phone. Many websites, Windows PCs, and forms still ask for JPG. JPEG is the same format, so a request to convert an iPhone photo to JPEG is a request for JPG.
Changing the camera to Most Compatible only affects photos you take after that. Pictures already in Photos stay HEIC until you convert each file. What is a HEIC file?
