When HEIC is the right output
HEIC uses HEVC/H.265 encoding — about 2× more space-efficient than JPG at equivalent quality. It's the default iPhone camera format since iOS 11. Support is narrower than JPG: iOS, macOS Big Sur+, Windows 11 (with a codec install), Android 10+ (with limitations). Convert to HEIC when destination is Apple-ecosystem storage / iCloud, or for archival compression of a large JPG library.