A slot is a placeholder inside a web component that users can fill with their own markup (see Using templates and slots for more information). This article explains how you can use the and elements to create a flexible template that can then be used to populate the shadow DOM of a. When working with Shadow DOM-enabled components, the element is a web platform native way to allow content projection into components. [HOST] › blog › introducing-shadow-dom-api. As you can see, slot-based composition is a powerful tool that allows widgets to pull in the page content without cloning or modifying the DOM. Slots allow to show elements from light DOM in specified places of shadow DOM. Note that when applying the restamp attribute to dom-if. The slotted element appears, but then doesn't disappear when the dom-if becomes false. . The slot is rendered correctly and everything appears to behave, except when flicking back and forth, once the earlier slot has been rendered. There are two kinds of slots: Named slots: