Display element over one with position: sticky

Question

I need to display a dropdown content over an element that has position: sticky set. Unfortunately manipulation with z-index didn't help much. The content shown on hover is still covered by next sticky element.

Full example presenting the problem with multiple applets: https://jsfiddle.net/tfkh2v0n/3/

Minimal example:

.applet-container {
  position: relative;
  z-index: 1;
}

.applet {
  position: relative;
  z-index: 2;
}

.sticky-header {
    top: 0px;
    position: sticky;
    background: #d1d1d1;
    z-index: 3;
}

.dropbtn {
  background-color: #4CAF50;
  color: white;
}

.dropdown {
  position: relative;
  display: inline-block;
  z-index: 4;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: gold;
  min-width: 160px;
  z-index: 5;
}

.dropdown-content a {
  display: block;
}

.dropdown:hover .dropdown-content {
  display: block;
  z-index: 5;
}

<div class="applet-container">
  <div class="applet">
      <div class="sticky-header">
        Sticky Header 
        <div class="dropdown">
          <button class="dropbtn">Dropdown</button>
          <div class="dropdown-content">
            <a href="#">Link 1</a>
            <a href="#">Link 2</a>
            <a href="#">Link 3</a>
          </div>
        </div>
      </div>
      <div class="content">Content 1 that will be displayed over</div>
  </div>
    <div class="applet">
      <div class="sticky-header">Dropdown content should be displayed over this sticky header</div>
  </div>
</div>

Answer 1

Get rid of all the z-index (you don't need any of them) and simply set z-index to the sticky element on hover.

.applet-container {
  position: relative;
  /*z-index: 1;*/
}

.applet {
  position: relative;
  /*z-index: 2;*/
}

.sticky-header {
  top: 0px;
  position: sticky;
  background: #d1d1d1;
  /*z-index: 3;*/
}

.dropbtn {
  background-color: #4CAF50;
  color: white;
}

.dropdown {
  position: relative;
  display: inline-block;
  /*z-index: 4;*/
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: gold;
  min-width: 160px;
  /*z-index: 5;*/
}

.dropdown-content a {
  display: block;
}

.dropdown:hover .dropdown-content {
  display: block;
  /*z-index: 5;*/
}

.sticky-header:hover {
  z-index: 1;
}

<div class="applet-container">
  <div class="applet">
    <div class="sticky-header">
      Sticky Header
      <div class="dropdown">
        <button class="dropbtn">Dropdown</button>
        <div class="dropdown-content">
          <a href="#">Link 1</a>
          <a href="#">Link 2</a>
          <a href="#">Link 3</a>
        </div>
      </div>
    </div>
    <div class="content">Content 1 that will be displayed over</div>
  </div>
  <div class="applet">
    <div class="sticky-header">Dropdown content should be displayed over this sticky header</div>
  </div>
</div>