background-attachment CSS property

Recently I came into and issue. I checked background size on Chrome devtools and it looked okay:

But then when I looked on the iPhone gadget: background looked horribly, it was zoomed:

After a small search I found explanation (http://caniuse.com/ – feat=background-attachment) . By the fact that mobile browser does not support background-attachment: fixed property. So Chrome devtools(51.0.2704.106 (64-bit) not always help to test your page on mobile browser properly.

This is code of example page:

So to solve the issue I needed to set background-size: 100% to set image to fit screen width.