You take a photo on an iPhone, copy it to a Windows laptop or attach it to an upload form, and it will not open. The file ends in .heic, and the form says the format is not supported. Nothing is wrong with the photo. It is simply stored in a format that much of the world still does not read by default.
What HEIC is
Since iOS 11 in 2017, iPhones have saved photos in HEIF, the High Efficiency Image File Format, with the picture inside compressed using HEVC, the same codec iPhones use for video. A file in that combination gets the .heic extension.
The reason Apple switched is size. HEVC is a far newer compression method than JPEG, which dates from 1992, and Apple's own figure is that a HEIC photo takes about half the space of a JPG of the same quality. On a phone that holds thousands of photos and backs them up to the cloud, that is a real saving. HEIC can also carry things JPG cannot, such as the depth map used for Portrait mode and 10-bit colour.
Why it will not open elsewhere
Inside Apple's world, HEIC is invisible: Photos, macOS Preview and Safari open it without comment. Outside, support is patchy.
- Windows can display HEIC, but only after installing two extensions from the Microsoft Store, one of which, the HEVC codec, is a small paid add-on. Many PCs have neither.
- Websites and forms frequently accept only JPG and PNG. Government portals, job applications and older content management systems are common examples.
- Older editing software may not read HEIC at all.
So the same file that looks perfect on the phone is unreadable for the person or system it was sent to.
Three ways to get a JPG
1. Change what the camera saves. In Settings, then Camera, then Formats, choose Most Compatible. From then on, new photos are saved as JPG. The cost is that every photo takes roughly twice the storage. This is the right choice if you regularly send photos to Windows users or upload them to forms.
2. Let the iPhone convert when it shares. In Settings, then Photos, the Transfer to Mac or PC option set to Automatic converts photos to JPG when they are copied to a computer by cable. Sharing through Mail and many apps also converts automatically. AirDrop between Apple devices keeps HEIC, because the receiver can read it.
3. Convert the files you already have. For photos already on your computer, or for when you need a specific file in JPG right now, a converter is quickest. The HEIC to JPG converter here does it in the browser. Safari decodes HEIC with the operating system's own support; other browsers load a WebAssembly build of libheif, the open-source HEIF library, the first time you use it. Several photos can be converted at once and arrive together in a ZIP.
What changes in the conversion
Converting to JPG means decoding the HEIC and encoding the picture again, so quality matters. At 90% the result is visually indistinguishable from the original for normal viewing, at the cost of a file around twice the HEIC's size. If the photo is going into a size-limited upload, run it through an image compressor afterwards, or reduce the dimensions, which saves far more than lowering quality.
One change is often an advantage. The new JPG is drawn from the picture's pixels, so the metadata in the original, including the GPS location where the photo was taken and the camera model, is not copied across. That is worth knowing in both directions: it protects your location when you share a photo of your home, and it means the date and place are gone if you were relying on them for organising. To see exactly what an original carries before you share it, open it in the image metadata viewer.
Which to choose
If you mostly stay inside Apple's ecosystem, keep HEIC: you get the storage saving and lose nothing. If you share constantly with Windows users or upload to forms, switch the camera to Most Compatible. For everything in between, keep HEIC on the phone and convert the handful of photos that need to travel. And if the destination is a website rather than a person, consider skipping JPG entirely: AVIF keeps most of HEIC's size advantage and every current browser displays it.