A QR (Quick Response) code is a two-dimensional matrix barcode made of black and white squares that stores data, most often a web address, which a phone camera or scanner reads. It was invented in 1994 by Denso Wave for tracking car parts.
Why it matters
QR codes bridge physical and online worlds: menus, tickets, payments, Wi-Fi sharing and product packaging all use them. Because a person cannot read the destination by looking at the pattern, they are also used in scams, such as stickers placed over legitimate codes or fake parking payment codes. Built-in error correction lets a code still scan when part of it is damaged or covered by a logo.
Example
A restaurant table card encodes https://example.com/menu. Scanning it opens that page. If the owner wants to change the destination later without reprinting, the code can point to a short redirect address that they control and update.
Common mistakes
- Printing the code too small or with low contrast, which makes scanning unreliable.
- Encoding a long URL with tracking parameters, which produces a dense pattern. Shorter data scans better.
- Scanning codes from stickers or unsolicited mail without checking the preview address.
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