HEIF

Every photo on a phone or computer exists as a file in storage. How that file is structured is determined by the file format. The best-known format for photos is called JPEG and dates back to 1992. HEIF is a considerably younger successor, published in 2015 by the standardization group MPEG. The abbreviation stands for High Efficiency Image File Format. The name says it all: at the same image quality, a HEIF image needs roughly half the storage space of the same image as a JPEG.

Why half the file size makes a difference

Storage space sounds like a solved problem. It isn’t. Modern phone cameras capture images at 48 megapixels, meaning 48 million pixels. Anyone who collects a few thousand such photos quickly fills up several gigabytes. Halving the file size lets twice as many memories fit on the same device.

The effect is even more important when uploading. Photos today move almost automatically into a cloud, meaning onto a provider’s servers on the internet. Smaller files upload faster and use less data on mobile networks. For providers like Apple or Google, this adds up across billions of images to substantial costs for storage and transmission.

HEIF can also do things that JPEG simply cannot. It stores true transparency, meaning see-through image areas. It can hold multiple images within a single file, such as a short motion sequence. And it supports greater color depth, so skies and skin tones are rendered without visible banding.

Video technology applied to still images

The trick behind HEIF is borrowed. The format uses the same techniques for compression, meaning shrinking the data, as modern video formats. Specifically, it usually contains the video standard HEVC, also known as H.265. A video has to compress enormous amounts of data, which is why a great deal of research has gone into such techniques since 1992. HEIF simply treats a photo as a video with a single frame.

The gain comes from the fact that HEVC describes image areas more cleverly than JPEG. Instead of storing each block individually, the technique often says: “This area looks like the one next to it, just a bit brighter.” Such predictions save data. JPEG doesn’t have this technique, because it comes from a time before such ideas existed.

A common misconception: HEIF and HEIC are not two different formats. HEIF is the container, meaning the shell of the file. HEIC is the file extension Apple uses when this shell contains HEVC-compressed data. As with JPEG, this is lossy compression: a tiny portion of the image information is permanently lost during saving, though normally it isn’t noticeable.

iPhone photos that a PC refuses to open

HEIF is most often encountered with the iPhone. Since iOS 11 in 2017, Apple has stored photos as .heic by default. Anyone who copies such files to an older Windows computer or uploads them to a school portal sometimes gets a message saying the format is not supported. In the iPhone settings, under “Camera,” you can switch to “Most Compatible,” which produces JPEG files again.

By now, though, support is widespread. Windows 11, macOS, Android, and all major browsers handle HEIF just fine. When sending via WhatsApp or uploading to Instagram, the services usually convert the image to another format automatically anyway.

In tech news, HEIF mainly comes up in comparisons with competitors. AVIF and WebP pursue the same goal but can be used royalty-free. HEVC, on the other hand, is patent-protected, meaning manufacturers must pay licensing fees. That’s precisely why Google favors WebP and AVIF on the web, while Apple sticks with HEIF. JPEG, however, isn’t going to disappear anytime soon, simply because it works everywhere.