I'm guessing HEIC.
JPEG-XL offers all the benefits of HEIF and more, while not being patent encumbered.
I'm also thinking the OP meant HEIC, but I know that it is not proprietary (though as noted patented), and wanted to make sure, as a lot of people of all sorts of assumptions/misconceptions about Apple.
HEIF/HEIC is based on H.265, so not Apple-only as Android supports it. (Recent Sony, Canon, Nikon, etc cameras all support the format as well.)
https://www.dpreview.com/articles/8980170510/how-hdr-tvs-cou...
> HEIF/HEIC is a broad standard, and the files from Canon and Apple are not cross-compatible with one another