What actually is a QR code?

It seems like QR codes are everywhere these days. They are simple enough to use, but what are they really? And how do they work? The creation of the QR code goes all the way back to Japan in 1994, where a car manufacturer called Denso Wave created these encoded pictures to help with inventory management. What they figured out was that by dropping the rigid limitations of barcodes, far more data could be stored on physical items, using even less space. Consider this simple barcode as an example:

It contains 12 characters, four letters and 8 numbers. If it contained twice as many characters, it would be twice as long. Now consider the same data encoded into the QR format:

This code also contains “ABCD12345678”, and it’s not noticeably smaller. What’s the big deal? Well, what about this one:

This code is the same size as the previous one, although it is noticeably busier. It should be though, since it contains an entire poem.

But how?

Firstly, alignment is key. Notice how every QR code always has these three squares in the corner? These are required so the reader can scan the code from any angle. A sensible requirement considering the history of QR Codes – how indeed would anyone determine the correct reading orientation for code on a spark plug or an exhaust pipe?

Now the reader knows where the bottom right of the code is, it will start to read the squares, a little at a time. Firstly, it identifies the “mode” the code is in (numbers, letters, data or kanji). Then it figures out how many characters are stored in the code, and finally the reading begins. It follows a path from the bottom right up until it reaches the top right square, then does the next column to the left, going back down to the bottom. This “snakes and ladders” reading pattern continues until it reaches a stop signal in the code. After that some extra bits of data are included for redundancy – this helps protect codes against damage. Once complete the reader returns the decoded text to the user or the application that requested it.

 

And that, at a very high level, is how QR codes work. If you’d like to know more feel free to reach out – at VividQR we never tire of discussing QR codes.