You can find them on posters at events, on the back of flyers from supermarkets, and since this year of course in the Coronacheck app: QR codes. Fifteen years ago these white squares with black dots were still special, now they are everywhere. But how exactly does a QR code work?
In fact, a QR code is nothing more than an old-fashioned barcode. These codes were invented in 1994 by Masahiro Hara, an engineer employed by auto parts manufacturer Denso.
Hara was looking for a way to make a lot of information quickly scannable. Normal barcodes are relatively limited: the EAN code that we use in the supermarket in the Netherlands consists of 13 digits. The largest barcodes can contain about 100 characters.
Much more data in a QR code
A QR code consists of many more dots, and can therefore store much more. The average QR has room for 7,089 numbers, or 4,269 numbers with letters.
And another advantage: you can make a QR code very small, without it becoming unreadable. So you don’t lose as much space on a QR as you do with an old-fashioned barcode.
Inspired by Japanese board game
Masahiro Hara was inspired by the old Japanese board game Go. The Go board has a large number of squares, on which players take turns placing stones.
One day, during lunch, Hara peered at his Go board full of black pebbles and realized: This is a very efficient way to pass on information. Putting the information in a square allowed you to store it both vertically and horizontally, instead of a barcode, which only works horizontally.
Denso shared the idea with other companies and released the patents, hoping to jointly set up a QR system. That’s why QR codes are now completely royalty-free for anyone to create and use.
So how exactly do they work?
Just like a Go board, a QR code consists of a lot of cells that can be filled with black. In the corners are one or more points that are slightly larger: these are there so that your camera quickly finds the code.
Each box next to these checkpoints can be a 1 or a 0 – black or white. Each cluster together forms one letter, number, or other character, depending on how many ones and zeros are together.
Your camera will start reading the black areas in the bottom right corner. There it is stated what kind of characters are in the rest of the QR code: are they numbers, numbers and letters, bytes or Japanese kanji characters?
The QR code then also ‘tells’ exactly how many characters there are in the code. The scanner then zigzags up and down and ‘reads’ the text or numbers in the code.
This is how a QR code works on a torn piece of paper
The last dots, on the far left of the block, are there to tell your smartphone what correction is being applied to the code, for situations such as when the paper is torn. This is done through a special algorithm. The stronger the error correction, the more information you have to put into the code.
There are even more patterns in a QR code that are included by default to aid in reading the code. For example, there are dots that indicate how a scanner should read a code when it is bent, and blocks at the top and left that tell you which standard version of a QR code it is. There are dozens of different versions in order of size: 21 by 21 pixels is the smallest, 177 by 177 pixels the largest.
Two different types
In terms of function, you can also divide QR codes into two different types, static and dynamic. Static codes are finished as soon as they are created. Think of a code for a business card, or your WiFi. No one can change these codes after they are finished.
More often you will have to deal with so-called dynamic QR codes. The destination of these codes can be changed quickly because there is not a lot of information in them.
nothing more than a link
In fact, a dynamic QR code is nothing more than a link that points to another link. For example, consider a menu at a restaurant that you can only view by scanning the QR code. Via the link method, the restaurant can quickly adjust the destination of the code without changing the code itself. They just need to change the URL that the link points to.
This method is also widely used with payment codes. Because although you can put a lot of information in a QR code, your banking transactions are still far too complex.
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