Technical··5 min read

What HEIC Is, Why iPhones Use It, and When to Convert

A short explainer on HEIC: where it comes from, why it gives smaller photos, why so many tools still don't open it, and how to convert when you need to send a photo somewhere else.

You take a photo on your iPhone, drop it into a website, and a polite error pops up: "file format not supported". Welcome to the HEIC conversion problem.

This article explains what HEIC actually is, why Apple defaults to it, why it's still awkward in 2026, and how to convert it without uploading your photos anywhere.

What HEIC is

HEIC is a container format. The actual image data inside is encoded with HEVC (also called H.265), the same video codec used in most 4K streaming. HEIC borrows that codec and applies it to a single frame instead of a video stream.

The file extension can be .heic or .heif (HEIF is the broader standard; HEIC is the HEVC-encoded subset). HEIF files can also wrap AVIF (AV1-encoded), but in practice if you see .heic on an iPhone, the contents are HEVC.

Apple shipped HEIC by default starting with iOS 11 in 2017. Since then, every photo your iPhone takes is HEIC unless you've explicitly switched to "Most Compatible" in Camera settings.

Why Apple chose it

At equal perceptual quality, HEIC files are typically 40–50% smaller than equivalent JPEGs. For a phone taking thousands of photos that sync to iCloud, that adds up. Both in storage and in upload time.

HEIC also supports useful features JPEG cannot:

  • Multiple images in one file (Live Photos, burst sequences).
  • Depth maps for portrait mode.
  • 10-bit colour depth and HDR.
  • Auxiliary alpha and image data.

Inside Apple's tightly integrated stack (Camera app, Photos.app, iCloud, AirDrop), these features are seamless. The trade-off is that HEIC is harder to read outside that ecosystem.

Why so many tools still trip on it

  • Patents. HEVC is patent-encumbered. Decoding/encoding requires licences from MPEG-LA, HEVC Advance, and Velos Media. Open-source projects, browsers, and free tools have historically avoided shipping HEVC support to avoid royalty exposure.
  • No native browser decode. Until very recently, no browser would render an HEIC tag. The situation is improving (Safari 17 supports it natively, others rely on JS/WASM), but assuming HEIC will display in <img> tags is still a mistake.
  • Legacy Windows. Windows 10/11 require an Extension from the Store to view HEIC, and that Extension is a paid download for the encoder side.
  • Uploaders that filter by extension. Plenty of forms reject anything that's not .jpg or .png by file-name check before they even read the bytes.

When you need to convert

  • Uploading a photo to a website that rejects .heic.
  • Sending a photo to someone on Windows or older Android.
  • Embedding a photo in a Word document or printable PDF.
  • Editing in software that doesn't yet read HEIC (some older Lightroom installs, GIMP without plugins, older Affinity).
  • Posting to a social platform that silently transcodes (and where you want to control the transcode quality yourself).

How to convert without losing quality

HEIC → JPEG is lossy in both directions. HEIC stored a lossy version of the original sensor data, and JPEG re-encodes it lossily again. To minimise visible loss:

  • Keep JPEG quality at 85–92. Below that, double-compression artefacts become visible. Above that, file size grows fast for small visual gain.
  • Resize before encoding only if you actually need a smaller pixel count. JPEG quality of a downsampled image is much better than a same-resolution low-quality JPEG.
  • For maximum quality archive, convert to PNG (lossless). The file will be 3–5× larger, but you keep every pixel from the HEIC decode.

Convert in your browser

AinnoBox uses libheif compiled to WASM to decode HEIC inside your browser. The decoded image is then re-encoded by the Canvas API as JPG (or PNG). No file leaves your device.

Two relevant tools:

If you want to skip the problem entirely

On iPhone, switch the default capture format:

  1. Settings → Camera → Formats
  2. Choose Most Compatible instead of High Efficiency

From then on, your iPhone will save photos as JPEG instead of HEIC. You lose the storage savings but gain universal compatibility. A fair trade if most of what you do with photos involves sending them somewhere outside Apple's ecosystem.

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