responsive image in bootstrap

1<img src="..." class="img-responsive">

1<img class="img-fluid" src="" alt=""> //This will make your image responsive

1<img src="fox.png" class="img-fluid" />

1In addition to our border-radius utilities, you can use 
2.img-thumbnail to give an image a rounded 1px border appearance.
3
4<img src="..." alt="..." class="img-thumbnail">

1<img src="..." class="rounded mx-auto d-block" alt="...">

1<!-- Circuler Image -->
2 <img src="cinqueterre.jpg" class="img-circle" alt="Cinque Terre"> 
3 
4<!-- Image With some border-raduis property  -->
5 <img src="cinqueterre.jpg" class="img-rounded" alt="Cinque Terre"> 
6 
7<!-- Image like thumbnail  -->
8 <img src="cinqueterre.jpg" class="img-thumbnail" alt="Cinque Terre">