A QR code is a square, black-and-white pattern that a phone camera can read in an instant. Most often it holds a web address, so scanning it opens a page without anyone typing. It can also hold plain text, Wi-Fi login details, a contact card or a pre-filled email. "QR" stands for Quick Response.
How a QR code stores and recovers data
The code was invented in 1994 by Denso Wave, a Toyota group company, to track car parts, and it is now an ISO standard. The three large squares in the corners tell the scanner where the code is and which way up it sits. The remaining small squares encode the data as binary, plus extra error-correction data. Thanks to that redundancy, a code can still scan when part of it is dirty, damaged or covered by a small logo; the highest error-correction level can recover roughly 30 percent of the code. More data means more, smaller squares, which is why a code holding a long URL looks denser and is harder to scan from a distance.
Static versus dynamic QR codes
A static code contains the final address directly. It never expires, but it can never change. A "dynamic" code contains a short link owned by a QR service, which redirects to your real page. You can change the destination and see scan counts, but if the service closes or your subscription lapses, every printed code stops working. A middle path is a static code pointing at a short address on your own domain that you redirect yourself, the same idea as a branded URL shortener.
Example: a restaurant table card
A restaurant prints a code on each table that opens its menu page. The URL includes UTM parameters such as utm_source=table, so analytics shows how many menu views came from inside the restaurant. The menu is a regular mobile-friendly web page, not a PDF, so it loads quickly and can be updated without reprinting the cards.
When QR codes are worth it
They shine where someone holds a phone but not a keyboard: flyers, packaging, shop windows, event signs, business cards, invoices. On a website itself they are mainly useful for moving a desktop visitor onto their phone, for example to download an app.
QR code mistakes
- Sending scans to a page that is not mobile-friendly. Every scan comes from a phone.
- Printing too small or with low contrast, such as light grey on white or inverted colours some scanners reject.
- Locking printed codes to a paid dynamic service without knowing what happens if you cancel.
- No hint what the code does. A short line like "Scan for the menu" gets more scans and more trust.
- Ignoring scams. Fake stickers placed over real codes are a known trick, so check public codes you own periodically.
Related terms
- URL shortener: keeps codes small and destinations editable.
- UTM parameters: measure scans in analytics.
- Landing page: where a campaign code should lead.
- Deep link: can send a scan straight into an app.