Is it possible for a site to prevent the page from loading and completely replace it?

Question

JavaScript

The idea is to
a) speed up a slow loading site that is not cached. That is, the extension works like a cache.
b) keep showing the site even if it crashes and becomes unavailable.
At the time of interception, the site itself does not need to be loaded, that is, the content is not needed. In any case, you need to give the user html from the extension memory and very quickly, without waiting for the download or canceling it.

Answer 1

Option 1. Caching proxy server
Option 2. New site, extension or just js. Difference from the previous option: the user does not download the URL of the original site, but yours