Here are some examples of what you can do with QR codes:
– Link to a website: https://your-website.com/some/page?with=parameters
– Share email address: mailto:your.name@gmail.com
– Share phone number: tel:+49123456789
– Share WLAN network password: WIFI:T:WPA;S:Your WLAN name;P:Your WLAN password;;
– Send SMS: smsto:+49123456789:Hi John, how are you?
– Send email: mailto:recipient@example.com?subject=Test email&body=This is a test email
– Add second factor to Google Authenticator: otpauth://totp/Issuer Name:alice@google.com?secret=JBSWY3DPEHPK3PXP&issuer=Issuer Name