If you've ever tried to upload an iPhone photo to a website, an old app, or send it to someone on Windows and gotten a confusing error or a file that just won't open, the cause is almost always the same: your iPhone saved it as HEIC, and whatever you're using doesn't understand that format.
Why iPhones use HEIC at all
HEIC (High Efficiency Image Container) compresses photos to roughly half the file size of an equivalent JPEG at similar visual quality — which matters a lot when you're taking hundreds of photos on limited phone storage. Apple made it the default camera format starting with iOS 11, and it's a genuinely better format from a pure compression standpoint.
The problem: almost nothing else supports it
No web browser can open a HEIC file directly. Most Windows photo viewers can't either, without installing an extra codec. Plenty of websites that accept photo uploads will simply reject a HEIC file outright or show a broken image icon. Since HEIC never became a universal web standard the way JPEG did decades ago, converting is usually the fastest path forward.
What actually happens during conversion
Converting HEIC to JPG decodes the image and re-encodes it in the older, universally-supported format. The trade-off is a somewhat larger file size for the same photo — that's the cost of HEIC's efficiency advantage going away. One thing worth knowing: most browser-based converters (this one included) don't carry over EXIF metadata like location or the exact time the photo was taken, so if you need that data preserved, keep the original HEIC as a backup.
Convert without installing anything
The HEIC to JPG converter runs entirely in your browser — no app, no account, and the photo is never uploaded to a server. There's also a HEIC to PNG version if you specifically need a lossless, alpha-capable format instead.