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). [HOST] › blog › introducing-shadow-dom-api. 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. 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: