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<body class="d-flex flex-column">
  <div id="page-content">
    <div class="container text-center">
      <div class="row justify-content-center">
        <div class="col-md-7">
          <h1 class="font-weight-light mt-4 text-white">Sticky Footer using Flexbox</h1>
          <p class="lead text-white-50">Use just two Bootstrap 4 utility classes and three custom CSS rules and you will have a flexbox enabled sticky footer for your website!</p>
        </div>
      </div>
    </div>
  </div>
  <footer id="sticky-footer" class="py-4 bg-dark text-white-50">
    <div class="container text-center">
      <small>Copyright &copy; Your Website</small>
    </div>
  </footer>
</body>
/* Sticky Footer Classes */

html,
body {
  height: 100%;
}

#page-content {
  flex: 1 0 auto;
}

#sticky-footer {
  flex-shrink: none;
}

/* Other Classes for Page Styling */

body {
  background: #007bff;
  background: linear-gradient(to right, #0062E6, #33AEFF);
}

              

External resources loaded into this fiddle: