QR codes require a border of a few pixels on some Android phones / cameras, this border is called the 'quite zone'.
The quiet zone is the empty margin or space surrounding all four sides of the QR code that separates the barcode from other elements in the image.
A quiet zone helps the QR reader accurately detect the QR code’s presence. It also helps determine from where the QR code begins and ends.
The size of the border is a variable which changes depending on the number of characters in your QR code and should be 4 or more modules. This can make the border look large on QR codes with only a few characters (like short links).