The problem, in one sentence
Since 2017, iPhones save photos as HEIC (High Efficiency Image Container) by default instead of JPEG — a format that compresses roughly twice as efficiently, which is great for storage but isn't understood by most non-Apple software, upload forms, and older Windows programs.
Why Apple switched to HEIC
HEIC is built on the same compression technology as modern video codecs, letting it store a photo at roughly half the file size of an equivalent-quality JPEG. For a phone shooting thousands of photos with finite storage, that's a meaningful win — Apple made it the default silently, and most iPhone owners never notice until they try to share or upload one of these files somewhere that doesn't recognize it.
How to tell if that's your problem
The signs are consistent: the file extension reads .heic or .HEIC, Windows Photos shows a gray placeholder icon instead of a thumbnail, an upload form rejects the file or shows a generic 'unsupported format' error, or a website simply refuses to accept the file at all despite it clearly being a photo.
Three ways to fix it
Pick based on your situation
- Convert once, when needed — the simplest fix for a single upload or email is converting the HEIC file to JPG in your browser, which takes a few seconds and needs no installation.
- Install HEIF support on Windows — the free 'HEIF Image Extensions' from the Microsoft Store lets Windows Photos preview and open HEIC natively going forward, useful if you deal with these files constantly.
- Change your iPhone's capture format — under Settings → Camera → Formats, switching from 'High Efficiency' to 'Most Compatible' makes your iPhone shoot JPEG directly, at the cost of roughly double the storage per photo.
Which fix should you actually use?
If this is a one-off — you need to upload a photo to a government portal, an old system, or attach it somewhere that rejected HEIC — converting the single file is faster than installing anything. If you constantly deal with a client's or a family member's iPhone photos, installing the Windows extension solves it permanently. If it's your own phone and you rarely need iPhone-specific features like Live Photos, switching capture format to JPEG avoids the problem at the source.