How do QR codes work?

Answer: A grid of black and white squares stores the data

A grid of black and white squares stores the data ✓ — Correct! A QR code is just a grid of black and white squares printed on paper or shown on a screen. The arrangement of those squares carries the information, with black and white standing in for the ones and zeros of binary data. Three larger squares in the corners let a camera figure out which way the code is facing, and built-in error correction means it still reads even if part of the grid is smudged or torn. Your phone snaps a picture, the software works out the pattern, and out comes a web address or a line of text.

A thin magnetic strip along the edge stores the data — Wrong. A QR code has no magnetic strip at all — it is only ink or pixels arranged in a grid. Nothing about it is magnetized, so there is no strip to swipe or read with a magnetic head; the data lives in the visible pattern.

A shiny hologram layer stores the data — Wrong. A QR code is not a hologram and has no shiny layer that stores anything. It is a flat printed pattern, and any ordinary camera can read it in normal light without special viewing angles or laser illumination.