SOURCE

<div class="sk-wave">
  <div class="sk-rect sk-rect1"></div>
  <div class="sk-rect sk-rect2"></div>
  <div class="sk-rect sk-rect3"></div>
  <div class="sk-rect sk-rect4"></div>
  <div class="sk-rect sk-rect5"></div>
</div>

body {
  background-color: #1abc9c;
}

.sk-wave {
  margin: 40px auto;
  width: 60px;
  height: 40px;
  text-align: center;
  font-size: 10px; 
}

.sk-wave .sk-rect {
  background-color: #FFF;
  height: 100%;
  width: 8px; 
  display: inline-block;
  -webkit-animation: sk-waveStretchDelay 1.2s infinite ease-in-out;
  animation: sk-waveStretchDelay 1.2s infinite ease-in-out;
}

.sk-wave .sk-rect1 {
  -webkit-animation-delay: -1.2s;
  animation-delay: -1.2s;
}

.sk-wave .sk-rect2 {
  -webkit-animation-delay: -1.1s;
  animation-delay: -1.1s;
}

.sk-wave .sk-rect3 {
  -webkit-animation-delay: -1s;
  animation-delay: -1s;
}

.sk-wave .sk-rect4 {
  -webkit-animation-delay: -0.9s;
  animation-delay: -0.9s;
}

.sk-wave .sk-rect5 {
  -webkit-animation-delay: -0.8s;
  animation-delay: -0.8s;
}

@-webkit-keyframes sk-waveStretchDelay {
  0%,
  40%,
  100% {
    -webkit-transform: scaleY(0.4);
    transform: scaleY(0.4);
  }
  20% {
    -webkit-transform: scaleY(1);
    transform: scaleY(1);
  }
}

@keyframes sk-waveStretchDelay {
  0%,
  40%,
  100% {
    -webkit-transform: scaleY(0.4);
    transform: scaleY(0.4);
  }
  20% {
    -webkit-transform: scaleY(1);
    transform: scaleY(1);
  }
}