How to Convert HEIC to JPG
HEIC is the default photo format on modern iPhones — more efficient than JPG at storing the same visual quality — but it's also the source of a very common frustration: a photo that opens fine on the iPhone that took it, and then fails to open (or displays as a broken file icon) practically everywhere else.
Why HEIC causes compatibility problems
HEIC is a newer format, and while Apple's own ecosystem (iPhone, Mac, recent versions of Windows with the right extension installed) handles it natively, plenty of older software, many websites, and a lot of non-Apple platforms simply don't recognize it. The photo isn't corrupted — the software just doesn't know how to read that particular format, which is a compatibility problem, not a quality one.
What's traded away by converting to JPG
HEIC generally achieves smaller file sizes than JPG at equivalent visual quality, so converting to JPG typically increases file size somewhat — the cost of trading HEIC's efficiency for JPG's much broader compatibility. For most everyday sharing purposes, this tradeoff is well worth it, since a photo that can't be opened at all is far more useless than one that's a bit larger than it strictly needs to be.
What's preserved
Visual quality converts faithfully — you're not losing meaningful detail in a well-done HEIC to JPG conversion, since both formats are capable of representing the photo at high quality; the practical difference between them is efficiency and compatibility, not achievable quality. Metadata like the date taken and location (if the photo has it) is generally preserved too, unless you specifically want to strip it for privacy before sharing.
Converting a whole camera roll at once
If you're moving a large batch of photos off an iPhone to a platform or device that doesn't handle HEIC, converting the whole batch to JPG in one pass avoids finding out about the compatibility issue one broken photo at a time — worth doing proactively before a big transfer rather than reactively after something fails to open.
HEIC to JPG converts iPhone photos directly in your browser, no software install required. If you specifically need transparency support instead, HEIC to PNG is the equivalent conversion to PNG. For a large batch, Compress Image can help offset the size increase from switching formats.