This is just ffmpeg powered and it looks like some support was added fairly recently.

https://trac.ffmpeg.org/ticket/6521

https://git.ffmpeg.org/gitweb/ffmpeg.git/commit/a0821345eb31...

The wasm build of libvips (the image processing library this thing uses) does not include HEIC because of the various patent issues:

https://github.com/kleisauke/wasm-vips/issues/3

It does support AVIF and JXL. Hopefully Apple will abandon HEIC hehe.

Agree adding HEIC support to vert.sh would be awesome. You can convert HEIF to JPG though using the ImageMagick mogrify command.

    mogrify -format jpg -quality 90 "$INPUT_FILE"

Yes, this is my most common web conversion. HEIC to JPG