iPhone Photo Formats: Camera, Transfer and Sharing Settings

The camera setting: High Efficiency or Most Compatible

The capture format is set under Settings, then Camera, then Formats. Apple's support article on HEIF and HEVC media names the two choices: High Efficiency and Most Compatible. High Efficiency stores photos as HEIF (the files end in .heic) and videos as HEVC. Most Compatible stores new photos as JPEG and new videos as H.264. Apple notes the choice appears only on iPhones and iPads that can capture HEIF and HEVC at all.

Two practical points follow from Apple's wording that all new photos and videos use the chosen format. First, the setting applies from the moment you change it; photos already in your library are not rewritten. Second, the library becomes mixed: older pictures stay HEIC, newer ones are JPEG, and the extension in a file manager tells you which is which. Videos change as well, so Most Compatible also switches video to H.264, which is the older and less efficient video format.

Apple states that HEIF and HEVC give better compression than JPEG and H.264 at the same visual quality, without giving a ratio. How much space you actually gain depends on what you photograph, so a month of shooting in each mode is the only reliable way to find out for your own use. The format comparison is covered in the HEIC and JPEG comparison.

Sharing: the file you send may not be the file you see

According to Apple, when you share media through methods such as AirDrop, Messages or email, it might automatically be shared in a more compatible format such as JPEG or H.264. The wording is "might", which matters: the conversion depends on the method and on what the receiving side supports, so you cannot predict the file type from the Photos app alone.

Sharing through iCloud keeps the original. Apple says media shared through iCloud Photos keeps its original format, resolution and frame rate. That makes a shared iCloud link the right choice when the recipient uses Apple devices and wants the original, and a poor choice when the recipient needs to open the file in a program that does not read HEIC.

The result is that two people can receive the same photo from you through different channels and end up with different formats. If a recipient reports that your picture will not open, ask what the file extension is before diagnosing anything else.

Copying photos to a computer by cable

Apple's article warns that when you import photos over USB, they might be converted to JPEG or H.264 along the way. To prevent the conversion, it tells you to tap Keep Originals in the Photos settings, which in current iOS versions sit under Settings, then Apps, then Photos. On older iOS versions the Photos settings were a top-level entry directly under Settings, so if you do not see Apps, look there.

The setting is commonly described as Transfer to Mac or PC, with Automatic as the other choice. I could not confirm the word "Automatic" in Apple's own articles, and menu labels shift between iOS versions, so look at what your screen offers rather than relying on a remembered name. What Apple does document is the effect: Keep Originals sends the files as stored, with no conversion.

Which one you want depends on the destination. Choose Keep Originals if you plan to edit the HEIC files or archive them. Leave conversion on if the computer is a Windows machine that cannot display HEIC and you want JPEGs to appear automatically.

iCloud Photos and originals on the phone

Apple's transfer article states that iCloud Photos always uploads and stores your original, full-resolution photos, and that you can keep full-resolution originals on each device or save space with device-optimized versions. The consequence for transfers: with iCloud Photos turned on and device-optimized storage in use, the phone may hold smaller versions of older photos, and Apple says that you must download the originals to the iPhone or iPad before importing them to a PC. A cable import of a library in that state will not give you full-resolution originals.

The same is true for any conversion you plan to do afterwards. Convert from the original rather than from a downsampled device copy, or the result is limited to the smaller image.

Which combination fits which situation

• Everything stays on Apple devices and in iCloud: High Efficiency for capture, iCloud Photos for storage, no further settings needed.
• You regularly hand photos to Windows or Android users or upload to forms: either switch capture to Most Compatible, or stay on High Efficiency and convert the few photos that need it. The first costs storage on every photo; the second costs a conversion step on some.
• You back up to a Windows PC by cable: decide between Keep Originals (exact files, HEIC) and conversion (JPEG, widely readable but one extra lossy step), and set it before the first big import.
• You edit photos in software that is a few years old: test one HEIC file first; if the program cannot open it, Most Compatible avoids the problem at the source.

Checking what an existing photo is

To see what the camera produced, look at the extension. In the Photos app the info panel typically shows the file name on iOS versions that display it, and a name ending in .HEIC means the High Efficiency format, while .JPG means JPEG. On a computer, the same file listing shows it directly. After a Most Compatible change, expect your library to show both kinds, with the switch point at the date you changed the setting.

When people complain that "iPhone photos will not open", the usual suspect is a mixed library: a handful of HEIC files among many JPEGs. Sorting a folder by type finds them quickly, and once you know which files are HEIC you can convert only those. Do this before an important deadline, not during it, because a rejected upload at the last minute is the usual way people discover the issue.

What the iPhone settings do not solve

The settings only change what happens to future photos and future transfers. They do not convert an existing folder of HEIC files, and they do not make a browser or a web form accept HEIC. For an existing file, you need a conversion step on a device whose browser can decode HEIC; the HEIC to JPG guide explains the details. If a website rejects a photo and you cannot tell why, work through the checks for rejected image files before changing any phone setting.