Why Are Your iPhone Photos .HEIC?

Two standards stacked on top of each other, which is why the naming confuses everyone.

HEIF is the container: the High Efficiency Image File Format, specified as ISO/IEC 23008-12, built on the same ISO Base Media File Format that MP4 uses. It is a box that holds images, sequences of images, and metadata.

HEVC is the codec that squeezes the pixels: High Efficiency Video Coding, ISO/IEC 23008-2, also known as H.265, the video codec standardized in 2013. A HEIC photo is, at the pixel level, a single still frame encoded the way a modern video file encodes one of its frames.

The extension tells you which combination you have. .heic is a HEIF file whose image data is HEVC in the Main or Main Still Picture profile. The more general .heif can hold other codecs. Run file on a photo straight off an iPhone and macOS says so out loud:

$ file photo.heic
photo.heic: ISO Media, HEIF Image HEVC Main or Main Still Picture Profile

Read the container brands on the same file and you get the rest of the story. An untouched 4032 × 3024 frame from an iPhone 15 Pro Max declares a major brand of “High Efficiency Image Format HEVC still image (.HEIC)” and compatible brands of mif1, MiHE, MiPr, miaf, MiHB, heic. That miaf is the Multi-Image Application Format, ISO/IEC 23000-22, and it is there because the file is not carrying one picture. Alongside the photo sits an auxiliary image tagged urn:com:apple:photo:2020:aux:hdrgainmap, the HDR gain map that tells a capable screen how far past SDR white to push each region.

That is the part people miss when they call HEIC “Apple’s JPEG”. It is not a compression tweak. It is a container designed from the start to hold a photo, a depth map, a gain map, a burst and an alpha channel together, where a baseline JPEG holds exactly one image and needs vendor extensions bolted on for anything else.

iCloud storage economics, mostly. Apple ships a small free storage tier and a camera whose resolution keeps climbing; cutting the bytes per photo is worth real money to Apple and real time to anyone syncing a library over a phone connection.

Apple’s own wording, from its HEIF and HEVC support document: “HEIF and HEVC offer better compression than JPEG and H.264, so they use less storage space on your devices and iCloud Photos, while preserving the same visual quality.” Note what that sentence does not say. It does not give a number.

The capability arrived with iOS 11 and macOS High Sierra 10.13, and it is hardware gated: capture requires iPhone 7 or later, iPad (6th generation) or later, iPad Air (3rd generation) or later, iPad mini (5th generation) or later, the 10.5-inch and 11-inch iPad Pro or the 2nd-generation 12.9-inch and later, or Apple Vision Pro. If your photos are HEIC, your phone is from 2016 or newer and has been shooting this way since the day you updated.

The number everyone repeats is “half the size”. Measured carefully it is closer to a third, and the careful part matters.

Comparing a HEIC and a JPEG by file size alone is meaningless unless the two look equally good, and “equally good” has to be measured rather than eyeballed. So: nine iPhone camera frames at 12 megapixels, each encoded to HEIC at quality 80 and then to JPEG across a quality sweep. For each image, a binary search found the lowest JPEG quality whose structural similarity score matched or beat the HEIC’s. Then the file sizes were compared at that point.

32.3% smaller at equal measured quality, with individual images landing between 55% and 74% of the JPEG size. And that is a conservative floor, not a best case, because the reference image used for scoring was itself a JPEG. A JPEG re-encode inherits its reference’s artifacts and scores flatteringly against it; HEIC gets no such advantage. On a genuinely lossless reference the gap would widen.

A second trap worth naming, because it produces the inflated numbers you see quoted elsewhere. macOS’s own sips tool defaults to HEIC quality 80 and JPEG quality around 95. Convert a folder both ways at defaults and HEIC looks 47% smaller. That comparison is not measuring the codec, it is measuring two different quality settings.

The practical version of all this: an untouched 12-megapixel iPhone HEIC in our test set was 1,512,980 bytes. Converted to JPEG with sips at its default it became 2,439,855 bytes, 61% larger, for a picture no one could tell apart. Across a folder of 500 photos, 605.9 MB of HEIC became 989.6 MB of JPEG.

Because HEVC is patent-encumbered, and decoding it costs the operating system vendor a license fee that JPEG stopped requiring long ago.

Windows makes the split visible. Microsoft’s own developer documentation for the HEIF codec states it directly: “Images stored in HEIF files with the .heic file extension are compressed using the HEVC format, and such files require the HEVC Video Extensions package to be installed. If the HEVC Video Extensions package is not installed, the HEIF Image Extension will not be able to read or write .heic files.” The HEIF half is a free Store download. The HEVC half is a separate, paid Store package. A Windows user being handed HEIC files is being handed a purchase decision.

Beyond Windows the picture is patchier still. Any desktop application written before 2017 has no idea what the format is, because it did not exist. Older Android builds, web upload forms, print kiosks, insurance portals and court-filing systems reject it as a matter of routine. Which is the whole reason the batch HEIC to JPG conversion question exists at all.

Two separate settings do two different jobs, and mixing them up is why people change one and see no effect.

To change what the camera records, open Settings, tap Camera, tap Formats, then tap Most Compatible. Apple describes the effect as capturing “photos and videos in JPEG and H.264 formats”. To go back, choose High Efficiency in the same place. This only affects photos taken from now on. Everything already in your library stays HEIC.

To change what leaves the phone over a cable, open Settings, tap Apps, tap Photos, then scroll down to the Transfer to Mac or PC section. Automatic converts HEIC to JPEG during the import. Keep Originals hands over the HEIC untouched. If you are on an iOS release old enough that Photos sits at the top level of Settings rather than under Apps, the same control is at Settings → Photos.

That second setting is the one doing the work when people credit Image Capture with converting their photos. Apple spells it out: “When you import HEIF or HEVC media from an attached iPhone or iPad into Photos, Image Capture, or a PC, the media might be converted to JPEG or H.264.” Image Capture is not converting anything. The phone is.

Probably not, and this is where most articles on this topic go soft. HEIC is the better format by every technical measure that matters. It stores the same picture in a third fewer bytes. It carries a real HDR gain map, so your photos look right on the display they were shot for. It supports 10-bit color, which JPEG in practice does not. It holds depth maps, bursts and transparency in one file. Switching to Most Compatible throws all of that away permanently, on every photo you take from that moment on, to solve a problem that happens when you hand a file to someone else.

Shoot High Efficiency and convert at the boundary. That is the correct shape of the answer, and the export is cheap: one Terminal line or one right-click, and only for the photos that need to travel.

Switching to Most Compatible is genuinely the right call in three cases:

• You hand photos straight off the phone to Windows users constantly and cannot get them to install a codec.
• Your workflow runs through software that predates 2017 and will not be updated.
• You shoot for a system that rejects HEIC on upload and you have no computer in the loop to convert.

Outside those, the storage saving compounds every day and the conversion cost is minutes per year.

If everything you own is Apple, the answer is that you never needed one. macOS, iPadOS and iOS all open HEIC natively, Preview edits it, Quick Look previews it, and Photos treats it as a first-class citizen. Converting your library to JPEG “just in case” would cost you disk space and the HDR gain map for no gain.

If you need one file to send to one person, use Preview. Open it, choose File → Export As…, pick JPEG, drag the quality slider while watching the live file-size readout, save. It is free, it is already installed, and it takes fifteen seconds. Our step-by-step HEIC to JPEG guide walks that through with screenshots.

An app like Smol earns its keep at the other end of the scale: hundreds of files, a quality target, a resize, a metadata strip, and a Finder right-click instead of a Terminal. That case is covered in detail, with timings for every free alternative, in batch converting HEIC to JPG on a Mac. If PNG rather than JPEG is what you were about to reach for, read converting HEIC to PNG first — for photographs it is almost always the wrong target. And if the reason you are converting is that a file is too large to send, the operation you want may be compression rather than conversion. Smol is a one-time $29 and processes everything on your own Mac.