Navbar Dropdown (Collapse) Is Not Working in Bootstrap 5

Why the navbar dropdown in bootstrap 5 doesn't work

Change this:

<a class="nav-link dropdown-toggle" href="#" id="navbardrop" data-toggle="dropdown"> Dropdown link </a>

To this:

<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">Dropdown Link</a>

Also add this:

<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.bundle.min.js" integrity="sha384-ka7Sk0Gln4gmtz2MlQnikT1wXgYsOg+OMhuP+IlRH9sENBO0LRn5q+8nbTov4+1p" crossorigin="anonymous"></script>

<head>
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC" crossorigin="anonymous">
</head>
<nav class="navbar navbar-expand-sm bg-dark navbar-dark">
  <!-- Brand -->
  <a class="navbar-brand" href="#">Logo</a>

  <!-- Links -->
  <ul class="navbar-nav">
    <li class="nav-item">
      <a class="nav-link" href="#">Link 1</a>
    </li>
    <li class="nav-item">
      <a class="nav-link" href="#">Link 2</a>
    </li>

    <!-- Dropdown -->
    <li class="nav-item dropdown">
      <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">Dropdown Link</a>
      <div class="dropdown-menu">
        <a class="dropdown-item" href="#">Link 1</a>
        <a class="dropdown-item" href="#">Link 2</a>
        <a class="dropdown-item" href="#">Link 3</a>
      </div>
    </li>
  </ul>
</nav>
<br>

<div class="container">
  <h3>Navbar With Dropdown</h3>
  <p>This example adds a dropdown menu in the navbar.</p>
</div>



<h1>Navbar</h1>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <div class="container-fluid">
    <a class="navbar-brand" href="#">Navbar</a>
    <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-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 me-auto mb-2 mb-lg-0">
        <li class="nav-item">
          <a class="nav-link active" aria-current="page" href="#">Home</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-bs-toggle="dropdown" aria-expanded="false">
                  Dropdown
                </a>
          <ul class="dropdown-menu" aria-labelledby="navbarDropdown">
            <li><a class="dropdown-item" href="#">Action</a></li>
            <li><a class="dropdown-item" href="#">Another action</a></li>
            <li>
              <hr class="dropdown-divider">
            </li>
            <li><a class="dropdown-item" href="#">Something else here</a></li>
          </ul>
      </ul>
    </div>
  </div>
</nav>

<!-- JavaScript Bundle with Popper -->
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.bundle.min.js" integrity="sha384-ka7Sk0Gln4gmtz2MlQnikT1wXgYsOg+OMhuP+IlRH9sENBO0LRn5q+8nbTov4+1p" crossorigin="anonymous"></script>

Why dropdown dont work in bootstrap5 navbar?

It's not working to toggle the dropdown because the anchor tag is attempting to navigate. Remove the url from the href...

     <li class="nav-item dropdown">
           <a href="#" class="nav-link dropdown-toggle" 
              data-bs-toggle="dropdown" 
              role="button" aria-expanded="false">LoginPage</a>
           <ul class="dropdown-menu">
               <li class="nav-item ">
                  <a href="http://localhost:8080/LoginPage/Bootstrap-34" class="dropdown-item">Bootstrap</a>
               </li>
           </ul>
     </li>

Note to future readers: Most Bootstrap 5 "dropdown not working" questions are caused by failing to use the new data-bs- attributes

Bootstrap navbar content not showing when collapsed

Here you go...

Change:

data-toggle="collapse" (Bootstrap 4) to data-bs-toggle="collapse" (Bootstrap 5)
data-target="#navbarNav" (Bootstrap 4) to data-bs-target="#navbarNav" (Bootstrap 5)

#navbarLogo {
  width: 10rem;
  height: auto;
}

.navbar-brand img {
  height: 50px;
  width: auto;
  padding-left: 30px;
}

#linkText {
  font-family: hdFontMedium;
  font-size: 1.5rem;
  font-weight: bold;
  text-align: center;
}

#navbarNav {
  justify-content: flex-end;
  align-items: center;
}

#navbarListItem {
  padding-left: 10px;
  padding-right: 10px;
}

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <!-- Bootstrap css-->
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-1BmE4kWBq78iYhFldvKuhfTAU6auU8tT94WrHftjDbrCEXSU1oBoqyl2QvZ6jIW3" crossorigin="anonymous">
  <link rel="stylesheet" type="text/css" href=/static/main.css>
  <link rel="stylesheet" href=/static/style.css>
  <link rel="shortcut icon" type="image/png" href="/static/media/favicon.png" />
  <title>Dimsum Siblings</title>
  <!--font-awesome including icon for shopping cart-->
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
</head>

<body>


  <nav class="navbar navbar-expand-lg navbar-light bg-secondary" id="navbar">
    <a class="navbar-brand navbar-left" href="/" id="navbarLogoLink">
      <img src="static/media/logoWithText.png" alt="" id="navbarLogo">
    </a>

    <button class="navbar-toggler m-auto" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav" aria-controls="#navbarNav" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
    </button>

    <div class="collapse navbar-collapse" id="navbarNav">
      <ul class="navbar-nav">

        <li class="nav-item active" id="navbarListItem">
          <a class="nav-link px-6" id="mainNavlink" href="">
            <h3 id="linkText">ABOUT US</h3>
          </a>
        </li>

        <li class="nav-item active" id="navbarListItem">
          <a class="nav-link px-6" id="mainNavlink" href="/dimsumshop">
            <h3 id="linkText">ORDER DIMSUM BOX</h3>
          </a>
        </li>

        <li class="nav-item active" id="navbarListItem">
          <a class="nav-link px-6" id="mainNavlink" href="">
            <h3 id="linkText">INSTRUCTIONS</h3>
          </a>
        </li>

        <li class="nav-item active" id="navbarListItem">
          <a class="nav-link px-6" id="mainNavlink" href="">
            <h3 id="linkText">CONTACT</h3>
          </a>
        </li>

      </ul>
    </div>
  </nav>

  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.bundle.min.js" integrity="sha384-ka7Sk0Gln4gmtz2MlQnikT1wXgYsOg+OMhuP+IlRH9sENBO0LRn5q+8nbTov4+1p" crossorigin="anonymous"></script>
  <script src="https://code.jquery.com/jquery-3.6.0.min.js" integrity="sha256-/xUj+3OJU5yExlq6GSYGSHk7tPXikynS7ogEvDej/m4=" crossorigin="anonymous"></script>

</body>

</html>

Bootstrap 5 Nav-bar collapse does not work

You have to change the data-toggle to data-bs-toggle and use data-bs-target attribute. Add the ID in the collapse div. That's all.

<button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#collapse" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="navbar-collapse collapse" id="collapse">

Bootstrap v5 dropdown is not working (no drop down menu)

You need to apply 2 changes:

data-toggle has been renamed to data-bs-toggle.

Second, add the dependency to popper.js:

<script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.9.2/dist/umd/popper.min.js" integrity="sha384-IQsoLXl5PILFhosVNubq5LC7Qb9DXgDA9i+tQ8Zj3iwWAwPtgFTxbJ8NT4GN1R8p" crossorigin="anonymous"></script>

Or use the bootstrap version that has popper compiled in according to https://getbootstrap.com/docs/5.0/getting-started/download/

bootstrap collapse navbar not working. whenever i press the icon in a smaller screen the menu does not open, how do i fix?

Assuming you are using Bootstrap 5, Some attributes are changed compared to bootstrap 4.
Change your code like this

<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
  <div class="container-fluid">
    <a href="./index.html" class="navbar-brand"><img src="./images/StoreLogo.png" alt="Home" width="70px" height="auto"></a>
    <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
      <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="navbarNav">
      <ul class="navbar-nav">
        <li class="nav-item">
          <a class="nav-link active" href="./index.html">Home</a>
        </li>
        <li class="nav-item">
          <a class="nav-link" href="./AboutUs.html">About Us</a>
        </li>
      </ul>
    </div>
  </div>
</nav>

Click here for more Info Documentation