The "clipboardchange" event fires whenever the system clipboard contents are changed either by a web app or any other system application. This allows web-apps like remote desktop clients to keep their clipboards synchronized with the system clipboard. It provides an efficient alternative to polling the clipboard(using Javascript) for changes.
Today, a web-app can monitor the system clipboard by polling and reading the clipboard through async clipboard API at regular intervals. For example, web based remote desktop clients like Chrome Remote desktop may read the clipboard contents for changes on every page focus event which is inefficient. Some Github links also suggests polling of clipboard being performed in Electron JS apps like (https://gist.github.com/LewdEwe-ErikWallace/d6e36f899a77a4f05e46388c254d014f). This feature aims to introduce an efficient way of notifying web apps when clipboard changes.