Bootstrap 4 navbar dropdown height is different - html

Question

I'm using a bootstrap navbar with a dropdown for the user menu.
The issue
I'm using this navbar as a blade template in laravel. On some pages the dropdown menu has the dimensions 160x63.39px and on some other pages 160x49px.
But the source code is the same on every page.
Does anybody know what reasons this issue could have?
Source
<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
<div class="container">
<a class="navbar-brand" href="http://127.0.0.1">Tool</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbar">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbar">
<ul class="navbar-nav mr-auto">
<li class="nav-item">
<a class="nav-link" href="http://127.0.0.1/dashboard">Dashboard</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="userDropdown" role="button" data-toggle="dropdown">Ticketsystem</a>
<div class="dropdown-menu">
<a class="dropdown-item" href="http://127.0.0.1/tickets/new">Neues Ticket</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="http://127.0.0.1/tickets">Alle Tickets</a>
</div>
</li>
</ul>
<ul class="navbar-nav ml-auto">
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="userDropdown" role="button" data-toggle="dropdown" aria-expanded="false">User</a>
<div class="dropdown-menu">
<form action="http://127.0.0.1/logout" method="post">
<input type="hidden" name="_token" value="#CSRF_TOKEN#">
<button type="submit" class="dropdown-item">Logout</button>
</form>
</div>
</li>
</ul>
</div>
</div>
</nav>

Answer 1

This is because different browsers have default CSS on some elements.
Best way to remove this is to add this CSS to your code:
* {
margin: 0;
padding: 0;
}
Or to use necolas.github.io/normalize.css