How do I scan a QR code from an image stored on iOS?

iOS 11 added the option to scan a QR code with the built-in camera app on an iPhone. However, I couldn’t find an option to scan a QR code from an image saved to my camera roll or otherwise already saved to Files and not something printed or physical external to the phone.

How can I scan a QR code from an image already saved on an iPhone?

The app QR Reader for iPhone on the App Store is quite a powerful QR code app. Check it out.

I use it infrequently, but I'm glad I have it in my toolbox.

Another reader that isn't scammy or tries to advertise / monetize your use is QRafter Pro and it's very solid over years of use.

Disclaimer: We're satisfied users of QR Reader/ QRafter for iPhone, and there are no financial or other connections between to TapMedia Ltd or QRafter.