I read the descriptions for the Dcentraleyes and LocalCDN addons which cache popular JS frameworks and page assets to enhance privacy and speed up pages that use them (since the assets were downloaded beforehand). Does Firefox have any built-in functionality to cache frequently used assets, or are there any addons that do so?
For instance, If I access Reddit.com a lot, I would want all the resources that all those Reddit pages have in common to be cached automatically to make loading pages from the domain faster.
Yeah, regular http cache is indeed a thing. However it’s more complicated because the web server can tell the browser how the returned content should be cached - if at all. So if, say, reddit servers ask the browser to not cache particular resource (for whatever reason) then it won’t be cached. I mean, the browser is free to do as it pleases, but I think in general browsers would do as the server asked and indeed not cache it.