Good news, every router is sold with a sticker that contains the Wi-Fi network information such as the Wi-Fi name and its password. You may have noticed a QR Code next to it. This QR Code is designed to simplify your connection to the Wi-Fi. Indeed, if you open your smartphone and scan the QR Code you will be automatically connected to the Wi-Fi of your device.

 
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Once you have changed the Network Name and Password of your router, the QR code will not work anymore as the connection information of your router will be different.