...This could be useful to block a user's interaction until they give you a response, or to confirm an action. See the HTML spec. This polyfill works on modern versions of all major browsers. It also supports IE9 and above. It can work when used inside Shadow DOM, but it's not recommended. The major limitation of the polyfill is that dialogs should not have parents that create a stacking context. The easiest way to solve this is to move your dialog element to be a child of body.