Client-side frameworks often focus on creating
single page apps. In this pattern, the entire website consists of a single HTML page with very little content, mostly the
On the other hand, if you did need server functionality (say you want to be able to save drawings to the server and re-open them on a different machine), you can combine your client-side app with a server-side API. It would provide authentication and persistent storage through a few endpoints, most likely communicating through sending JSON as requests and responses.
This approach - offloading heavy computation to the browser instead of the server means servers don’t need to work as hard. The benefit is they can be less powerful machines and serve more users while consuming less power, and generating less waste heat. This is why Google Docs, Microsoft 360, Facebook, and other big players have been pushing as much of their site’s computational needs to the client for years.