Edit in JSFiddle

<!DOCTYPE html><html class=''>
<head><script src='//production-assets.codepen.io/assets/editor/live/console_runner-079c09a0e3b9ff743e39ee2d5637b9216b3545af0de366d4b9aad9dc87e26bfd.js'></script>
<script src='//production-assets.codepen.io/assets/editor/live/events_runner-73716630c22bbc8cff4bd0f07b135f00a0bdc5d14629260c3ec49e5606f98fdd.js'></script>
<script src='//production-assets.codepen.io/assets/editor/live/css_live_reload_init-2c0dc5167d60a5af3ee189d570b1835129687ea2a61bee3513dee3a50c115a77.js'></script>
<meta charset='UTF-8'>
<meta name="robots" content="noindex">
<link rel="shortcut icon" type="image/x-icon" href="//production-assets.codepen.io/assets/favicon/favicon-8ea04875e70c4b0bb41da869e81236e54394d63638a1ef12fa558a4a835f1164.ico" />
<link rel="mask-icon" type="" href="//production-assets.codepen.io/assets/favicon/logo-pin-f2d2b6d2c61838f7e76325261b7195c27224080bc099486ddd6dccb469b8e8e6.svg" color="#111" /><link rel="canonical" href="http://codepen.io/shane935/pen/EGCyn" />


<style class="cp-pen-styles">input {
  padding: 10px 8px;
  width: 100px;
  border-radius: 12px;
  border: 1px solid gray;
  transition: 300ms width;
  outline: 0;
  font-size: 16px;
}
input:hover {
  width: 120px;
}
input:focus {
  width: 300px;
  transition: 600ms width;
}
</style></head><body>
<input type="text"  placeholder="Search"/>

</body></html>