HEIC to JPG: Why iPhone Photos Refuse to Open, and What Converting Changes

HEIC stands for High Efficiency Image Container; the container format itself is HEIF, and the picture inside is compressed with HEVC — the same family of coding that H.265 video uses. HEVC is roughly twice as efficient as the JPEG standard it replaced, which is why Apple switched the iPhone camera default to it in iOS 11 and why the files are so much smaller for the same visual quality.

The word container is doing real work there. A single HEIC file can hold the still image, a depth map from the portrait camera, an HDR gain map that reconstructs highlights above standard white, the still frame and short video of a Live Photo, and thumbnail previews. That richness is invisible in most viewers but explains why a HEIC is not simply 'a photo' the way a JPG is: conversion has to decide what to keep.

Support is split by platform, not by file quality. Apple devices read HEIC natively — macOS previews it, Photos edits it, Safari displays it. Windows 10 and 11 need the HEIF Image Extensions from the Microsoft Store, and decoding HEVC video content can require the separate HEVC Video Extensions, which some machines must pay for. Android has read it since Android 9, but individual gallery and messaging apps vary. Browsers are the weakest link: a web page asking for an image upload usually accepts JPG and PNG and rejects HEIC outright.

The other half of the confusion is thumbnails. Because a HEIC carries its own embedded JPEG preview, some file browsers show a correct thumbnail and then fail when you actually open the file — the viewer was showing the thumbnail, not decoding the photo. If a file previews fine but opens blank, that is usually what happened.

The pixels survive, re-encoded once into JPEG. That is a second lossy generation only if the HEIC itself was lossy, which it almost always is — in practice the difference is invisible at normal viewing size, because the first encode was at high quality. What changes is everything around the pixels.

High dynamic range is the biggest casualty. Modern iPhones capture more range than a standard JPEG can hold, and store the extra highlights in a gain map. Converters that ignore the map produce a flatter, sometimes clipped image: skies that were smooth acquire white patches, backlit faces lose detail. Transparency, where present, is filled with a background colour because JPG has no alpha channel. Depth data and Live Photo motion are dropped. EXIF is usually carried across — including GPS coordinates, which is worth remembering before posting a photo of your home.

The file also gets bigger. HEVC is efficient enough that the equivalent-quality JPG is often around twice the size, which surprises people who assume conversion compresses.

Convert from the original HEIC, never from a screenshot or a re-saved copy — those start from an already-recompressed image. If the photo is going to be edited further in an image editor, convert to PNG instead of JPG so the editing passes do not stack lossy generations; the file will be larger, but it stays clean until you export a final JPG.

Watch orientation. Phone photos are stored landscape with an EXIF rotation flag, and a converter that copies the flag without applying it produces a sideways image. If the result is rotated, the tool ignored the tag. And if the destination is a website rather than a person's desktop, consider WebP or AVIF instead of JPG — both are smaller at equal quality and are supported by every current browser.