Bootstrap4 media query directly taken mobile view even file opening on laptop - css

Question

i'm using bootstrap 4 on my new project and my laptop Touch + Mouse enabled windows when i tried to use bootstrap its automatically showing mobile format in desktop. how to solve this? below i attached screenshot
Note : Bootstrap 3 is working fine. this problem only on bootstrap4
My Code:
<header>
<nav class="navbar navbar-dark bg-dark">
<a class="navbar-brand" href="#">
<img src="images/logo.png" class="d-inline-block align-top" alt="">
</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarTogglerDemo02" aria-controls="navbarTogglerDemo02" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarTogglerDemo02">
<ul class="navbar-nav mr-auto mt-2 mt-lg-0">
<li class="nav-item active">
<a class="nav-link" href="#">Home</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Link</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Disabled</a>
</li>
</ul>
<form class="form-inline my-2 my-lg-0">
<button class="btn btn-outline-success" type="button">Main button</button>
</form>
</div>
</nav>
</header>

Answer 1

You need to use the correct HTML as stated in the documentation of bootstrap
Navbars require a wrapping .navbar with .navbar-expand{-sm|-md|-lg|-xl} for responsive collapsing
You neglected this class, so it is always collapsed.
It is not enough to just change the CSS from bootstrap 3 to 4 you also have to change the markup quite a bit.