Why HEIC exists and why it causes so much friction
HEIC is Apple’s implementation of HEIF (High Efficiency Image File Format), a container standard that can store images compressed with HEVC (H.265) video compression technology — the same codec family used for 4K video streaming. Applying video-grade compression to still photos allows HEIC to store a photo at roughly half the file size of an equivalent-quality JPG, which matters enormously at phone scale: a typical iPhone user takes thousands of photos, and halving their storage footprint is a real, tangible benefit for both on-device storage and iCloud sync speed. Apple switched HEIC on by default starting with iOS 11 in 2017.
The friction comes from licensing. HEVC decoding requires patent licenses that cost money per device or per software install, and many platforms — most of Windows out of the box, most of Android, virtually every web browser, and a huge amount of older or budget software — never added support, either for cost reasons or because HEIC simply predates their last major update. The result is a format that works great within Apple’s ecosystem and creates a compatibility wall the moment a photo leaves it: emailing a HEIC photo to someone on Windows, uploading it to a site that only accepts JPG/PNG, or opening it in most photo-editing software outside Apple’s own apps will fail or show a broken thumbnail.
What conversion actually does
Converting HEIC to JPG requires two separate steps: decoding the HEIC container to get the raw pixel data (this needs an HEIF/HEVC decoder, which is why this tool loads a WebAssembly-based decoder specifically for this conversion, rather than using the browser’s native image support, since browsers generally can’t decode HEIC either), and then re-encoding those pixels as a standard JPG. Because both HEIC and JPG are lossy formats, this is a lossy-to-lossy conversion — some quality is technically lost in the process, but re-encoding at a high JPG quality setting keeps that loss well below the threshold of visible difference for virtually any normal photo.
What you gain and lose by converting
You gain universal compatibility: JPG opens natively on every operating system, every browser, every image viewer, and every website upload form built in the last twenty-five years without exception. You lose some of HEIC’s storage efficiency — expect the converted JPG to be roughly 1.3-1.5x the size of the original HEIC for a comparable visual result, since JPG’s older compression scheme simply needs more bytes to represent the same visual quality. For photos you’re keeping purely for long-term personal storage, staying in HEIC (or converting to a more efficient modern format like WebP or AVIF, if your destination supports it) saves space; for photos you need to share, print, upload, or edit outside Apple’s ecosystem, converting to JPG removes the compatibility risk entirely.
A note on batches from AirDrop or iCloud
When you export or AirDrop many photos off an iPhone at once, they typically arrive as a folder of individual .HEIC files. This tool’s batch mode is built for exactly that case — drop the whole folder’s contents in, and each photo converts independently, so you can go from “a folder from my phone that only opens on my phone” to “a folder of ordinary JPGs” in a single pass, without installing a codec pack or converter app.