How make responsive background on div

Question

I am trying to make responsive background images on a div element but it does not work.

Here is my CSS:

.block-main{
  background: url(images/ohdaihiep/bg1.png) center center/cover no-repeat;
  min-height:863px;
}

Answer 1

You can use vh and vw to make it responsive:

fiddle to play around.

.block-main {
  background: url(http://placekitten.com/301/301)center center/cover no-repeat;
  height: 100vh;
  width: 100vw;
}

<div class="block-main">

</div>