HTML - <menu>

Context menu

HTML content

<!-- A <div> element with a context menu -->
<div contextmenu="popup-menu">
  Right-click to see the adjusted context menu
</div>

<menu type="context" id="popup-menu">
  <menuitem>Action</menuitem>
  <menuitem>Another action</menuitem>
  <hr>
  <menuitem>Separated action</menuitem>
</menu>

CSS content

div {
  width: 300px;
  height: 80px;
  background-color: lightgreen;
}

Result

Menu button

HTML content

<!-- A button, which displays a menu when clicked. -->
<button type="menu" menu="popup-menu">
  Dropdown
</button>

<menu type="context" id="popup-menu">
  <menuitem>Action</menuitem>
  <menuitem>Another action</menuitem>
  <hr>
  <menuitem>Separated action</menuitem>
</menu>

Result

Toolbar

HTML content

<!-- A context menu for a simple editor,
    containing two menu buttons. -->
<menu type="toolbar">
  <li>
    <button type="menu" menu="file-menu">File</button>
    <menu type="context" id="file-menu">
      <menuitem label="New..." onclick="newFile()">
      <menuitem label="Save..." onclick="saveFile()">
    </menu>
  </li>
  <li>
    <button type="menu" menu="edit-menu">Edit</button>
    <menu type="context" id="edit-menu">
      <menuitem label="Cut..." onclick="cutEdit()">
      <menuitem label="Copy..." onclick="copyEdit()">
      <menuitem label="Paste..." onclick="pasteEdit()">
    </menu>
  </li>
</menu>

Result