Answers for "navbar-expand-lg class"

responsive navbar bootstrap 4

<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="#">swipeit</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarSupportedContent">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Link</a>
      </li>
      <li class="nav-item dropdown">
        <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
          Dropdown
        </a>
        <div class="dropdown-menu" aria-labelledby="navbarDropdown">
          <a class="dropdown-item" href="#">Action</a>
          <a class="dropdown-item" href="#">Another action</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="#">Something else here</a>
        </div>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled" href="#">Disabled</a>
      </li>
    </ul>
    <form class="form-inline my-2 my-lg-0">
      <input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
      <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
    </form>
  </div>
</nav>

dissect the navbar bootstrap

<h1><a name="responsivebtn"></a>A responsive navigation bar with toggle button</h1>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent_resptb" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="navbarSupportedContent_resptb">
        <div class="navbar-nav">
            <a class="nav-item nav-link active" href="#">Item1 Active</span></a>
            <a class="nav-item nav-link" href="#">Item2</a>
            <a class="nav-item nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Item3 Disabled</a>
        </div>
    </div>
</nav>

navbar-expand meaning

ISSUES with menu size in Ipad pro menu not collapsing, sugestion for bootstrap navbar-expand-md