If you work in the transport and logistics sector, then GS-1 Code 128 is crucial. SSCC and GTIN codes are used extensively. Search on either and you will see example labels. In manufacturing, Datamatrix is very popular as the code is very dense, for example, printing on circuit boards and ICs. Both GS128 and Datamatrix are used extensively in B2B applications. For B2C, QR codes are commonly used. Most phones can scan QR codes effectively, and these codes typically contain a URL.
I have only one instance where a product has a mixture of all barcode types; the client, a heating manufacturer, uses Datamatrix during production. GS1 is used for the shipping labels. On the finished product label, they have a QR code linked to the product manual, and the Datamatrix containing product code, serial number and manufacture date. The latter is for use by their service engineers. On a separate label, they have a QR code for customer registration.
In the case of GS1 codes, the human-readable is always present below the code. For the 2D symbologies (Datamatrix and QR), this is much less common. I have several customers using Code 128, and while the human-readable information is often present, it will not be linked to the barcode.
For all of my customers, they don't use any web front-end we have produced to print the barcodes. We always generate barcode labels using third-party software, Seagull Software's BarTender (
https://www.seagullsoftware.com/). This approach makes any application we produce independent of the label design and printing method. Using BarTender, we are 100% confident that the barcodes will be correct and comply with industry standards.
The only application I can think of where we have generated the barcode within our applications is for ticketing. This was to enable the client to send unique invitations to their customers and scan the code from the email at the venue. Consider Amazon; they extensively utilise barcodes within their supply chain; however, you will struggle to find barcodes on their website. The most common are a QR code to download their application, and a Datamatrix code generated for a labelless return.