How to resize an image to fit in the browser window?

Question

This seems trivial but after all the research and coding I can\'t get it to work. Conditions are:

1. The browser window size is unknown. So please don\'t propose

Answer 1

I know there's already a few answers here, but here is what I used:

max-width: 100%;
max-height: 100vh;
width: auto;
margin: auto;