Why your iPhone photo will not open
Since iOS 11, iPhones save photos as HEIC — a container using modern compression that stores the same picture in roughly half the space of a JPG. On the phone this is invisible; the problem starts the moment the file travels.
Windows needs paid codecs to open it, older laptops and office machines show a broken icon, and most upload forms — job portals, government sites, college admission systems — validate the extension and reject anything that is not JPG, PNG or PDF outright.
Apple knows, which is why AirDrop and email convert on the way out. The HEIC that reaches you by USB cable, Google Drive or WhatsApp document-mode skipped that conversion — and that orphaned file is exactly what this tool is for.
JPG or PNG, and what quality to pick
JPG is the right answer for photographs, which is what iPhone shots are. At 90 percent quality the conversion is visually indistinguishable from the original for prints, forms and sharing, at a fraction of PNG's size.
PNG is lossless, and for a photograph that mostly buys you a file several times larger. Choose it when the image will be edited repeatedly afterwards, or when it contains hard-edged graphics — a screenshot saved as HEIC, for instance.
For upload portals with size limits, convert here first and then, if the JPG is still over the cap, run it through the image compressor. Converting and compressing in one lossy step after another is how photos turn to mush — do each once, deliberately.
What conversion keeps and what it cannot
The pixels come across at full resolution — a 12-megapixel HEIC becomes a 12-megapixel JPG. Nothing is resized or cropped, and the visual quality loss at high JPG settings is genuinely below what you can see at normal viewing sizes.
Some of HEIC's party tricks have no JPG equivalent. Live Photo motion, depth maps used for portrait-mode editing and certain wide-gamut colour information belong to the format; the converted file is the still image as it appears, which is what every portal wants anyway.
A file that fails to convert is usually not a real HEIC — renaming a file does not change its insides — or is damaged from an interrupted transfer. Re-copy it from the phone and try again before assuming the photo is lost.