What is a .heif file?

You have a .heif file — the container format behind HEIC. While HEIC specifically uses HEVC compression, HEIF (High Efficiency Image File Format) is the broader container that can hold images encoded with different codecs. Think of HEIF as the box and HEVC as one possible thing inside it.

HEIF can store single images, image sequences, depth maps, alpha channels, and auxiliary data — all in a single file. It's based on the ISO Base Media File Format (the same container family as MP4 and MOV). Apple uses the HEIC variant (HEIF + HEVC compression) as the default iPhone photo format. AVIF is another variant (HEIF + AV1 compression). The container itself is format-agnostic.

Apple Preview and Photos handle HEIF natively on macOS. GIMP (free) can open HEIF files with the appropriate plugin. For compatibility, convert to JPG or PNG — most of the time when you encounter a .heif file, it's an iPhone photo that should have been shared as .heic or converted to JPG.