How Do QR Codes Work?

Learn how QR codes work and why they are able to hold so much information and why custom QR codes are possible.

Make a code, scan the code

A person or company, uses a QR code generator to make a QR code that leads to readable, interesting content which they post somewhere it is likely to get scanned. When a consumer comes along, they take out their smart phone, open the QR reader application that came preinstalled on their phone or they downloaded from some kind of application store, and scan the code. The consumer spends more time on the company's page and is more likely to make a purchase or sign up for something, or interact with the company or person in some way then someone who saw a URL or a catch phrase in an ad. That's the essentials.

But what about the technology behind QR codes, how does it work?

Two Dimensions of Information

QR codes are a lot like the UPC barcodes that are found on every item in the grocery store. The difference between UPC barcodes and QR codes is that QR codes hold information in both the vertical and horizontal directions, while UPC barcodes only hold information only in the horizontal direction. This means that QR codes can hold a lot more information. Approximately 350 times more information.

This information is held in the modules of the code. (The black and white dots.) There are 40 “Versions.” The word version refers to the size of the code symbol in modules. A version one code is 21 modules by 21 modules. A version 40 code is 177 by 177. To go up a version, you add four modules to each side of the symbol. The more modules a code has, the more information it can store.

The physical size of a QR code can be adjusted by changing the size of its modules. This is usually the method that QR code generating sites use to change the size of the QR code symbol.

Error Correction and Customization

QR codes were developed to withstand the wear and tear of a factory and can be used even if they are dirty or damaged because they employ Reed Solomon code. Reed Solomon code is a type of mathematical error correction code that is commonly used in music CDs. On many QR generating sites there are four levels of error correction available to someone creating a QR code. The lowest level of correction offers 7% correction and the highest offers 30%. The most commonly used level of correction is 15%. In order for the symbol to be scannable, you need twice as much error correction code as the amount of code that needs to be corrected. It is because of the error correction capabilities of QR code that a low level of customization is available to QR code users. Users can put small text or pictures into their codes and the codes will still work.