QR codes assume a phone pointed at something else. When the code is on your own screen - a login QR in an email, a code in a PDF, a Wi-Fi QR someone pasted in chat - the usual dance is photographing your monitor with your phone, then emailing yourself the result.
The phone route
It does work: open Camera on your phone, point it at the screen, tap the notification. If the result is meant to end up on the phone - a login, an app link - that's even the right answer. The absurd part is when the link is meant for the Mac you're already sitting at.
Decode it in place
Text Capture reads QR codes the same way it reads text: press the hotkey, drag over the code, and the decoded content - a URL, Wi-Fi credentials, plain text - is on your clipboard, ready to paste into the browser or wherever it was headed.
One practical note from the app's own FAQ: capture just the code. If the selected region contains ordinary text alongside the QR code, the text wins and the code is ignored - a tight drag around the square is all it takes.
Free on the Mac App Store, fully offline - the code and its contents never leave your Mac.
FAQ
Can a Mac scan a QR code without a camera?
Yes - a QR code is data drawn as pixels, and an on-screen capture can decode it directly. No camera involved.
What kinds of codes does it read?
QR codes with any of the usual payloads: URLs, text, Wi-Fi credentials. The decoded text is copied as-is to the clipboard.
Why did my capture return text instead of the QR contents?
The region included readable text next to the code, and text takes precedence. Capture only the code and it decodes.