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The title and the first paragraph mention QR Code but the rest of the essay says barcode. Which is/are etched on the phones?

What is a QR code if not a 2D barcode?

barcodes use vertical bars

Sort of like how one might say 2D arrays.

> A matrix code, also termed a 2D barcode (although not using bars as such) or simply a 2D code,

barcode is not the preferred term because they don't use bars. A QR code is called a matrix code.

So confidently incorrect.