Learn how to use the camera on your iPhone to scan a QR code.
How to Scan QR Code on iPhone
Use Camera in iOS11 to Scan QR Codes
iPhone User Guide - Apple Support
iPhone 13 : How to Scan a QR Code (NO APP NEEDED)
iOS 12: How to use the Control Center scan QR code shortcut on iPhone - 9to5Mac
If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support
Reach the top of the iPhone screen with one hand - Apple Support
Can't Scan QR Codes with iPhone / iPad Camera? Here's a Fix
Use Siri on iPhone - Apple Support
QR code to open a song in Apple Music, Spotify, etc : r/shortcuts