Answers for "how to add a background image in bootstrap 4"

add background image in bootstrap 5

<div class="has-bg-img bg-purple bg-blend-screen">
  <h4>Background blend mode: Multiply</h4>
  <img class="bg-img" src="...">
</div>

bootstrap create full screen background image

.wrapper{background: url('/assets/64531/green_suburb.jpg') no-repeat   center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;}