How a QR code works and why each code is unique

How a QR code works and why each code is unique

With the arrival of the first smartphones and the generalization of the internet connection, the QR code was an improved version of the classic barcodes of a lifetime. Its most common use was to include a URL, since scanning them with our mobile took us to a certain web page.

In its day, it was a very common practice in digital marketing actions of companiesAlthough their use was not so widespread today, they have now become fashionable again as a result of the crisis caused by COVID-19.

Surely it has not gone unnoticed by sitting on a terrace, the absence of letters in favor of a QR code attached to the table through which we can see the menus available in the restaurant.

The “new normal” has made us resume contact with this old acquaintance, but Do you really know how a QR code works? If the answer is negative, then this post is for you.

QR Structure

What is a QR code and how does it work?

Let’s start with the most basic. A QR code is a two-dimensional, square-shaped barcode capable of storing encoded data through a text file or file. Also known as Quick Response Code, usually contain a URL in most cases.

For practical purposes, these codes are reduced to simple images that we can scan with our mobile camera. If you have noticed, these consist of a series of modules and patterns in black and white that make them unique given the incredible number of possible combinations. These are its specifications:

  • Position stop patterns: made up of three delimiters that allow the QR reader to know where the code content is.
  • Alignment pattern: this is another extra delimiter to know the orientation of the code.
  • Synchronization lines: thanks to these lines the reader can know the size of the symbols inside the body.
  • Variable information: here we find the information referring to the version of the QR code that is being used and the format line that determines the level of error correction.

In some cases, boxes are also usually added on the outside to give it a somewhat more aesthetic and personalized shape, but the reader does not collect this information.

Setting up QR codes

We have already seen that QR codes are a combination of black and white patterns, which houses a coded text file inside. This text file can reach contain a huge amount of characters as you can see below:

  • Numbers – Up to 7,089 characters
  • Alphanumeric data – Up to 4,296 characters
  • Binary – Up to 2,953 bytes
  • Kanji / Kana – Up to 1,817 characters

In addition, to facilitate reading speed, QR codes incorporate an error correction system, which are grouped by levels to categorize the recoverable data.

  • Level L 7% of codewords can be restored.
  • Level M 15% of codewords can be restored.
  • Level Q 25% of codewords can be restored.
  • Level H 30% of codewords can be restored.

This system that we are talking about, that allows correcting up to 30% of errors, is used so that the QR code can be read by our camera, even if it is damaged or has poor clarity. Which ultimately enables almost immediate read speed. In fact, as you will have seen more than once, access to the content of a QR code is quite fast.

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