The web messenger in Freshchat also known as the conversations widget, is used to deliver a convenient and contextual conversational messaging experience for customers. The web messenger loads within an iframe on  your website. So it cannot be pulled from an external source when your site is down.

You can loading the Freshchat web messenger asynchronously. This loads the widget without any dependance on the website.

The asynchronous code also reduces the load time of the site.