Starting with iOS 11 and continuing through iOS 13, Apple changed the default camera image file format for photos and videos to High-Efficiency Image File Format (HEIF) for images and sequences of images. For photos, that means the original images on your iPhone are stored as HEIC files instead of JPG.
If you take a HEIC picture on your iPhone and send it to a friend who has a Windows PC, older Android phone, or even an older Mac, they won’t be able to view it.
Here’s how to change your default image file format.
STEP 1 On a compatible iOS device running iOS 11 or later, launch Settings.
STEP 2 Tap Camera.
STEP 3 Tap Formats.