Bootstrap class: .text-*-center

<p class="text-center">Center aligned text on all viewport sizes.</p>
<p class="text-sm-center">Center aligned text on viewports sized SM (small) or wider.</p>
<p class="text-md-center">Center aligned text on viewports sized MD (medium) or wider.</p>
<p class="text-lg-center">Center aligned text on viewports sized LG (large) or wider.</p>
<p class="text-xl-center">Center aligned text on viewports sized XL (extra-large) or wider.</p>