QR code using html and css

To center a container you can use any of these: flex box , css grid or margin-block: auto

Oh, hello!

I was checking your code and I have some points to put here: Nice Work, congrats! :) The first thing is that you could use [text-align: center] on the ".container" at CSS to center your <img/> or you can turn the ".container" into [display: flex] and to him the attribute align-items: center, there are many ways to center things that are inside the parents.

The second, to center all the container, you could use position: relative with top:50% left:50% and transform: translate(-50%, -50%) or use margin: auto, or transforming your body tag into display: flex, there are many forms to do it too, even I don't know what is the right, I think that depends of situation.