Bootstrap class: .justify-content-*-center

<div class="d-flex justify-content-center">
  <div class="p-2">Flex item 1</div>
  <div class="p-2">Flex item 2</div>
  <div class="p-2">Flex item 3</div>
</div>

<!-- responsive variations -->
<div class="d-flex justify-content-sm-center">...</div>
<div class="d-flex justify-content-md-center">...</div>
<div class="d-flex justify-content-lg-center">...</div>
<div class="d-flex justify-content-xl-center">...</div>

Preview

Flex item 1
Flex item 2
Flex item 3

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