Why Apple switched
HEIC stores roughly the same photograph in about half the space a JPG needs.
On a phone holding several thousand pictures, halving the storage is not a
rounding error — it is the difference between running out and not. Apple made
it the camera default in iOS 11, back in 2017, and every photo your phone has
taken since is almost certainly a .heic file.
It can also do things JPG cannot: image sequences like Live Photos, transparency, and richer colour information. Inside Apple's world it is straightforwardly the better format.
The setting, and where it lives
On the iPhone, open Settings → Camera → Formats. There are two options:
- High Efficiency — the default. The camera writes HEIC.
- Most Compatible — the camera writes JPG instead.
Choose Most Compatible and the problem stops happening to new photos. There is no confirmation dialog and nothing to undo; you can switch back at any time.
The catch nobody mentions
The setting is not retroactive. It changes what the camera writes from that moment on and does nothing whatsoever to the photos already in your library. If the reason you went looking for this setting is a folder of holiday photos that will not open on a PC, changing it does not help with those at all.
That is worth saying plainly because the advice you will find elsewhere often stops at "change the setting", which quietly leaves people thinking the backlog has been dealt with. It has not.
Should you actually change it?
It depends on how often the problem bites.
Leave it on High Efficiency if your photos mostly stay inside Apple's world — viewed on the phone, backed up to iCloud, shared with other iPhone users. You keep the storage saving and rarely notice the format.
Switch to Most Compatible if you regularly send photos to people on Windows or Android, upload to forms that reject HEIC, or work with software that cannot read it. Storage is cheaper than repeatedly fixing files one at a time.
One thing that does not change either way: AirDrop and the Photos app usually convert to JPG automatically when sharing to something that needs it. The trouble tends to start when you pull files off the phone by cable or from a backup, where no such conversion happens.
The photos you already have
Those need converting, and the setting cannot do it. Converting to JPG is the usual answer — it opens anywhere, with no plugin and no explanation. If the photos are going into a document or will be edited again, PNG keeps every pixel exactly; if they need to arrive as one document, PDF puts a whole set into a single file, one photo per page.
The converter on this site runs inside your browser, so a folder of family photographs never leaves your machine on the way to becoming JPGs. That matters more here than it does for most file types.