<div class="info">This is a slightly changed srcset demo by <a href="https://media.kulturbanause.de/blog/2014/09/responsive-images/srcset-sizes-3.html">kulturbanause.de</a>. The images are just borrowed.</div>
  <img src="https://media.kulturbanause.de/blog/2014/09/responsive-images/medium.jpg" srcset="https://media.kulturbanause.de/blog/2014/09/responsive-images/small.jpg 320w, https://media.kulturbanause.de/blog/2014/09/responsive-images/medium.jpg 600w, https://media.kulturbanause.de/blog/2014/09/responsive-images/large.jpg 900w" sizes="100vw" alt=""> 

.info {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
  padding: 1rem;
  background: #efefef;
  border: 1px solid #ccc;
  margin-bottom: 1rem;
}
img {
  height: auto;
  max-width: 100%;
}