📱 How QR Codes Work

Why they still scan when partly covered, and how QR phishing works.

QR codes show up everywhere — payments, Wi-Fi setup, sharing a URL. Here's how they actually work and what to watch for.

How a QR code stores information

A black-and-white grid encodes text, a URL, Wi-Fi credentials, or similar as binary data. The three large squares in the corners (finder patterns) establish orientation and position, and the arrangement of dark and light cells in the grid is the actual data.

Why it still scans when partly damaged

Reed-Solomon error correction is built in, allowing up to 30% of the data to be recovered (depending on the error-correction level) even with a logo placed in the center or part of the code torn off.

Why QR phishing ("quishing") is a real risk

Because a QR code's destination URL can't be previewed by eye before scanning, it's vulnerable to "quishing" attacks — a fake payment QR pasted over a real one, or a malicious sticker placed on top of a legitimate code. Get in the habit of checking the URL preview before opening it after a scan.

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