how to center div bootstrap w3schools code example

Example 1: align center inner div using bootstrap

<div class="container">
  <div class="row justify-content-md-center">
    <div class="col col-lg-2">
      1 of 3
    </div>
    <div class="col-md-auto">
      Variable width content
    </div>
    <div class="col col-lg-2">
      3 of 3
    </div>
  </div>
  <div class="row">
    <div class="col">
      1 of 3
    </div>
    <div class="col-md-auto">
      Variable width content
    </div>
    <div class="col col-lg-2">
      3 of 3
    </div>
  </div>
</div>

Example 2: html center body

body {
  display:flex; flex-direction:column; justify-content:center;
  min-height:100vh;
}

Example 3: html center body

body {
max-width: max-content;
margin: auto;
}