Convert HEIC to AVIF

HEIC is an ISO container holding pictures compressed with HEVC, and HEVC is encumbered by several overlapping patent pools. That is the whole story of why a format that shipped on every iPhone from 2017 is still awkward everywhere else: a decoder costs money to license, so software vendors either paid, waited, or leaned on the operating system to do it for them.

AV1, which AVIF uses, was designed by the Alliance for Open Media specifically to avoid that. It is royalty-free by charter, its decoder is in every current browser, and nobody has to negotiate anything to read one. If the goal is a library that will still open on hardware and software you have not chosen yet, that difference is worth more than any number of kilobytes.

It is not a rewrap, even though the two files are structurally cousins — both are ISO base media containers, the same box-and-atom layout as an MP4, differing in what is inside. The HEVC data cannot be relabelled as AV1, so the picture is decoded all the way to raw pixels and compressed again from scratch.

That means one further generation of lossy compression, at quality 82. On a photograph of a person, a street or a landscape you will not see it side by side at normal size. Where a second generation shows first is in the places the first one already struggled — smooth sky gradients, out-of-focus backgrounds, and the block edges around high-contrast detail. Convert a dozen of your own worst-case pictures and look at those areas before deciding.

Getting the originals out is a step people underestimate. In the Photos app, selecting pictures and choosing Share then Export Unmodified Original gives you the HEIC as the phone wrote it; a plain share sheet or an AirDrop to a non-Apple machine may hand over a converted JPEG instead, and converting that to AVIF would be a third generation for no reason.

The same trap exists on the desktop side. On iOS, Settings then Photos has a "Transfer to Mac or PC" choice between Automatic and Keep Originals — Automatic silently converts HEIC to JPEG on the way out over a cable. If you are migrating a library deliberately, set it to Keep Originals so that what you convert here is the file the camera made.

HEIC is a multi-image container. A burst is many pictures in one file, a Live Photo pairs a still with a short sequence, and some editing workflows keep the unedited original alongside the edited version. This conversion takes the first image — the one the phone displays and the one anybody means when they point at the file — and writes that.

Everything else in the container is not carried into the AVIF. AVIF itself can hold animation and multiple images, so this is a limit of the conversion rather than of the target format. If a Live Photo’s motion is something you want to keep, export it from Photos as a video and keep that beside the still, because no image conversion is going to do it for you.

Nothing from the metadata block crosses. The capture date, the camera and lens, the exposure settings and the GPS coordinate are all absent from the output, because the conversion decodes to pixels and encodes again and there is no path for the block to travel.

For a library migration this is the single most important sentence on the page, and it cuts hard. A photo library organised by date is organised by metadata, and a folder of AVIF files with no capture dates is a pile rather than a library. Export the metadata separately — Photos can produce it, and so can exiftool — or keep the HEIC originals as the record and treat the AVIF set as the readable copy. Do not convert and delete.

A HEIC from an iPhone can carry ten bits per channel, and AVIF as a format goes to twelve, so on paper this is one of the few conversions where the target has room to spare. The pipeline here does not use it: the picture is decoded to eight-bit RGBA and encoded from that, so ten bits in becomes eight bits out.

The same applies to colour space. iPhone photographs are tagged Display P3 and no profile is written into the AVIF, so a viewer will treat the values as sRGB and the most saturated colours will sit back slightly. For a library of ordinary photographs this is a subtle shift; if wide-gamut colour is the reason you shoot on the phone, this conversion is not the way to preserve it.

AVIF is the slowest encoder on this site by a wide margin, and that is inherent to AV1 rather than a shortcoming of the implementation: the codec buys its compression with a very large search, and the search takes time. A single 12-megapixel photograph takes seconds rather than the fraction of a second a JPEG takes.

Multiply that by four thousand pictures and a library migration becomes an afternoon rather than a coffee break. It runs on your own processor, so nothing is queued behind anyone else, but it is worth converting in batches of a few hundred and leaving the tab alone while it works. Start with one batch, check the output, then commit the rest.

Browser support is settled, and support elsewhere is not. Older photo managers, some desktop image viewers, most photo frames, printing kiosks, and a good many upload forms have never heard of AVIF and will refuse it as flatly as they refuse HEIC. Trading one format nobody can open for another format nobody can open would be a poor migration.

The honest test is to list what will actually read the library — a browser-based gallery, a NAS with a modern viewer, a Linux desktop — and check those specific things with one converted file before converting the set. If the list includes anything old, keep a JPG copy of the pictures that need to be handed to other people, and use AVIF for the bulk that lives on your own storage.

This is the case where the privacy property stops being a talking point and becomes the deciding factor. A photo library is the most personal set of files most people own, and a bulk conversion means every one of them passing through whatever tool you chose. Here the HEIC is decoded by libheif in the page and the AVIF encoder runs in the same tab; no request carries an image.

Confirm it before you trust it with the whole set: open the developer tools, watch the network tab through one conversion, and see that nothing goes out. Then disconnect from the internet and convert another, which is the version of the test that leaves no room for interpretation.

The safe shape is three layers rather than one conversion. Keep the HEIC originals on a drive you do not touch, since they are the only copies with the capture data and the full quality. Generate the AVIF set as the working library, which is small and opens everywhere that matters to you. Export the metadata to a sidecar or a catalogue so the dates are recoverable independently of any file format.

Then delete nothing for a year. Formats and software both move, and the cost of keeping the originals is a few hundred gigabytes on a disk that is cheap, against the cost of discovering in eighteen months that the whole library is one generation down and undated.