how to get my footer to the bottom of the page using css

CSS
#page-container {
  position: relative;
  min-height: 100vh;
}

#content-wrap {
  padding-bottom: 2.5rem;    /* Footer height */
}

#footer {
  position: absolute;
  bottom: 0;
  width: 100%;
  height: 2.5rem;            /* Footer height */
}<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
.footer {
   position: fixed;
   left: 0;
   bottom: 0;
   width: 100%;
   background-color: red;
   color: white;
   text-align: center;
}
</style>
</head>
<body>

<h2>Fixed/Sticky Footer Example</h2>
<p>The footer is placed at the bottom of the page.</p>

<div class="footer">
  <p>Footer</p>
</div>

</body>
</html>
Source

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