Questo è stato taggato come bootstrap 3, ma forse questo sarà utile: In Bootstrap 4.0.0 (non beta): All'interno della classe col, utilizzare
<div class="col text-center text-md-left">
"text-center "centra il testo per tutte le dimensioni della finestra, quindi aggiunge" text-md-left "o" text-md-right "per cambiarlo sopra sm. Potresti renderlo "text-sm-left", "text-lg-left" o qualsiasi altra cosa. Ma averlo impostato per centrare sempre prima lo imposta.
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<link href="//netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.css" rel="stylesheet">
<body>
<footer>
<div class="container">
<div class="row">
<div class="col-xs-12 col-sm-6 text-center text-md-left">
<p>
© 2015 example.com. All rights reserved.
</p>
</div>
<div class="col-xs-12 col-sm-6 text-center text-md-right">
<p>
<a href="#"><i class="fa fa-facebook"></i></a>
<a href="#"><i class="fa fa-twitter"></i></a>
<a href="#"><i class="fa fa-google-plus"></i></a>
</p>
</div>
</div>
</div>
</footer>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
duplicati di http://stackoverflow.com/questions/18602121/change-text-align-responsively-with-bootstrap-3 – Lee
https://github.com/twbs/bootstrap/issues/21698 –