Why your computer cannot open these files
Since iOS 11, iPhones save photos as HEIC by default. It is a genuinely better format: the same photo takes roughly half the space of a JPEG at the same visual quality. The problem is everywhere that is not an Apple device.
Windows needs the HEVC Video Extensions from the Microsoft Store, which costs money on most machines. Android support depends on the manufacturer. Plenty of web upload forms, university portals and insurance claim systems simply reject the extension. So a file that opens instantly on the phone that took it becomes unusable the moment you move it.
PDF sidesteps all of it. Every operating system, every browser, every printer and every upload form made in the last twenty years accepts a PDF.
HEIC and JPEG, side by side
| HEIC | JPEG | |
|---|---|---|
| Typical size, 12 MP iPhone photo | 1.5 to 2.5 MB | 3 to 5 MB |
| Opens on Windows out of the box | No | Yes |
| Opens on Android out of the box | Depends on the phone | Yes |
| Can go into a PDF unchanged | No | Yes |
| Stores depth, Live Photo, HDR gain map | Yes | No |
| Accepted by upload forms | Often not | Always |
The last row is why people end up here. HEIC is the better file and the worse format to send anyone.
Stopping your iPhone from making HEIC in the first place
If you keep hitting this, change the setting instead of converting every time. On the phone, open Settings, then Camera, then Formats, and pick Most Compatible. New photos come out as JPEG. Photos you already took stay HEIC.
There is a second setting worth knowing. Under Settings, Photos, scroll to Transfer to Mac or PC and choose Automatic. iOS then converts HEIC to JPEG on the way out over a cable. Set to Keep Originals, it hands over the raw HEIC and you get this problem on the other end.
Batching a whole export
If you dumped a folder off the phone, select the lot and drop it in at once. The files are converted in the order they appear in the list, and you can move any of them with the arrows before you export. One photo becomes one page.
A phone browser will handle 20 to 30 HEIC files in one go. A laptop will do a few hundred but will take a minute or two, because each one is a full decode. If a batch stalls, split it in half rather than retrying the same batch.
For anything you do regularly, the app is the better tool: it reads HEIC natively instead of shipping a decoder into a web page, and there is no daily cap.