Technical criteria - a short guide...
Currently, the main interface for displaying qr-codes is the print media. But why?
You can still rely on reading habits, because of the "personal nature" of print publications. Therefore, the placement of the code is also a piece of evidence, whether on advertising material, information publications, magazines or other newspapers.
It is well known that a generic example of a website address may not be easy to remember or manually enter on a display device, but the code is easy to read. Print media are therefore an excellent medium if there is no physical barrier to reading. Its surface treatment, the size and colour of the code and the quality of the content behind the code, even in colour, can all influence successful scanning.
Already at the pre-press stage, you need to be aware of basic limitations, mainly the information density carried in the code and the size of the print. In a 2x2 cm code on a business card, it is not a good idea to compress large amounts of data, as this will result in a "denser" code with smaller squares, which is not readable by all cameras sufficiently.
For coloured and object codes (e.g. logo or background) the situation gets more complicated. Poorly chosen colour components and "distracting" surroundings are also not favourable to reading. For example, inverse code cannot usually be scanned, the colour of the code must always contrast with the background colour.
Downloading and reading the generated qr code is easy, but it takes some skill to create. The more complex the elements encoded, the greater the likelihood of worse quality when zoomed in. This is where the importance of size and the place it will be held come into the picture.
The role of the design in the qr code
Then: once the target group has been defined, colour can also play a significant role in success. It is important to know that the code is generated in RGB colour space by the generator, while the print media requires CMYK. A discrepancy in colour is possible during the conversion process because the printing colour space does not reproduce all RGB colours correctly - this is especially true for blue, for example, which can easily turn purple during printing. On a somewhat comforting note, material produced on digital presses can generally print well from RGB colour space - but don't let relativity fool your sense of caution.
Before mass production, it is not a bad idea to request a proof print of the page or product bearing the code and check it. This will tell you for sure if you have done a good job in the design. This can be a very important, preventive moment for a correction to avoid a possible error.