HEIF, HEIC and AVIF explained
HEIF (High Efficiency Image File Format) is a container defined by MPEG. What’s inside depends on the codec: HEIC files hold HEVC-compressed images (what iPhones save), while AVIF files hold AV1-compressed images. Both are HEIF under the hood. HEVC encoding isn’t available in browsers, so this tool writes AV1 into the HEIF container.
If the software you’re targeting specifically requires HEVC-coded .heic files, a native app is needed. For the web, an AVIF file is the most widely displayed modern format, and GIF to PNG is the safest universal choice.
Related conversions
Going from iPhone photos to GIF? HEIC to GIF decodes HEIC in any browser. To move a GIF onto an iPhone as something that moves, see GIF to Live Photo or GIF to MOV.