Apple used to have a spectacular record with stable formats: see HFS+. Unfortunately, over the last several years, that's gone out the window. Mojave can't re

Apple used to have a spectacular record with stable formats: see HFS+. Unfortunately, over the last several years, that's gone out the window. Mojave can't read some Big Sur volumes, even though both are using "Apple File System". HEIC image formats coming out of iPhones have changed /several/ times in the past couple years: witness the scrambling by the libheif project as they find out they can't read images from the latest iDevice. Apple's in-device conversion to JPEG is lossy, but I don't expect you will notice. Most of the metadata it's retained (at least with the current iOS), and I couldn't see egregious artifacting. I'd personally keep the original and hope tooling keeps up with Apple shenanigans, but disk is cheap, and if you're worried at all, use `sips` (if you're on a Mac), the built-in "compatibility mode" conversion, or `heif-convert` to transcode to JPEG. (Source: building support for HEIC in PhotoStructure)