<div class="container mt-3">

  <div class="demo-size-1">

    <form method="post" action="" class="input-group">

      <div class="form-outline">

        <input type="search" id="search" class="form-control">

        <label class="form-label" for="search">Enter keywords to search for</label>

      </div>

      <button type="button" class="btn btn-primary">

        <i class="fas fa-search"></i>

      </button>

    </form>

  </div>

</div>

​

<div class="container mt-3">

  <div class="demo-size-2">

    <form method="post" action="" class="input-group flex-nowra">

      <div class="form-outline">

        <input type="search" id="search" class="form-control">

        <label class="form-label" for="search">Enter keywords to search for</label>

      </div>

      <button type="button" class="btn btn-primary">

        <i class="fas fa-search"></i>

      </button>

    </form>

  </div>

</div>

.demo-size-1 {

  width: 200px;

}

​

.demo-size-2 {

  width: 300px;

}

​