<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title> CSS Border Hover Animation </title>
</head>
<body>
  <div class="container">
  <button class="btn-3"><span>Hover Me</span></button>
  </div>
</body>
</html>
*, *:after, *:before {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}
body{
  font-family: 'PT Sans', sans-serif;
  display: table;
  width: 100%;
  background: rgba(0,0,0,0.09);
}
.container{
  display: table-cell;
  vertical-align: middle;
  text-align: center;
  height: 100vh;
}
button{
  display: inline-block;
  position: relative;
  background: none;
  border: none;
  color: #fff;
  font-size: 18px;
  cursor: pointer;
  margin: 20px 30px;
  background: rgba(0,0,0,0.06);
}
span{
  display: block;
  padding: 25px 80px;
}
button::before, button::after{
  content:"";
  width: 0;
  height: 2px;
  position: absolute;
  transition: all 0.2s linear;
  background: #fff;
}

span::before, span::after{
  content:"";
  width:2px;
  height:0;
  position: absolute;
  transition: all 0.2s linear;
  background: #fff;
}
button:hover::before, button:hover::after{
  width: 100%;
}
button:hover span::before, button:hover span::after{
  height: 100%;
}

span::after{
  height:50%;
}
.btn-3::after{
  right:0;
  bottom: 0;
  width:30%;
  transition-delay: 0.6s;
}
.btn-3 span::after{
  transition-delay: 0.4s;
  right: 0;
  bottom: 0
}
.btn-3::before{
  right: 0;
  top: 0;
  transition-delay: 0.2s;
}
.btn-3 span::before{
  transition-delay: 0s;
  left: 0;
  top: 0;
}

.btn-3:hover::after{
  transition-delay: 0s;
}
.btn-3:hover span::after{
  transition-delay: 0.2s;
}
.btn-3:hover::before{
  transition-delay: 0.4s;
}
.btn-3:hover span::before{
  transition-delay: 0.6s;
}

External CSS

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External JavaScript

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