Bootstrap5 Bootstrap3

Bootstrap4:

Comes with .no-gutters out of the box. source: https://github.com/twbs/bootstrap/pull/21211/files

<div class="container">
  <div class="row no-gutters">
    <div class="col-6">
      <div class="p-3 border bg-light">...</div>
    </div>
    <div class="col-6">
      <div class="p-3 border bg-light">...</div>
    </div>
  </div>
</div>