What is a HEIC file?
HEIC is a modern photo format used by iPhones. Files are smaller than JPG, but many websites and older computers can't open them.
Why Apple uses it
HEIC stores a photo in roughly half the space of a JPG with similar quality, so your phone holds more.
Why it causes trouble
Government sites, job portals and older Windows PCs often reject it. Converting to PDF or JPG solves that.
How to get JPG instead
On your iPhone, open Settings, then Camera, then Formats, and choose Most Compatible. This only affects new photos.