I always wondered
What actually happens when you scan a QR code?
The Simple Answer
Your phone's camera reads a pattern of black and white squares and turns it back into text, usually a web address. Then your phone shows you that text and asks if you want to open it. The code itself does nothing.
A QR code is a way of writing text so that a camera can read it quickly. That text can be a web address, a Wi-Fi network name and password, a contact card or a plain message. The code only stores the characters. Nothing happens until you, or your phone on your say-so, acts on them.
Where it came from
The QR code was invented in 1994 by Masahiro Hara at Denso Wave, then a division of the Japanese company Denso. Ordinary barcodes held little, and people had asked for a code that could store more, including Japanese characters. The name stands for quick response, because the aim was a code that could be read very fast. Denso Wave says one code can hold about 7,000 digits.
Why it still scans when it is scuffed
Part of every code is spare information that lets a scanner rebuild what is missing. There are four levels, called L, M, Q and H, and the higher the level, the more damage the code can survive. Denso Wave says level M, which can repair about 15 percent, is the one most often chosen. That is why a code on a worn sticker or a crumpled receipt can still work.
What to check before you open it
Because a code is only text, a scammer can write a harmful web address into one as easily as a harmless one. The Federal Trade Commission warns that scammers hide harmful links in QR codes, sometimes sticking their own code over a real one. Its advice is simple.
- Look at the web address your phone shows before you open it, and watch for misspellings or switched letters.
- Do not scan a code in an email or text you were not expecting, especially if it urges you to act now.
- If you already entered a password on a page you reached that way, change it, and change it anywhere else you used it.
QR Code Generator: Make a code for a web address, Wi-Fi network or contact, and see exactly what text it holds. The code is made in your browser.