Would you do this please :

Type in the address bar about:config and press Enter (promise to be careful, if asked)

Type in the search bar : browser.cache

And look for the preferences :

browser.cache.disk.enable and browser.cache.memory.enable

Change their values to false

Then close and restart Firefox.

Note : It's best not to set "browser.cache.memory.enable" to "false" when you use Private Browsing mode, as this might cause performance issues.

network.http.use-cache is a pref in older versions of Firefox. So that article is incorrect or not written for the Quantum version of Firefox 57+.

You should leave the memory cache enabled. Firefox needs some caches in order to work properly. If you want to disable the disk cache then you can consider to use Private Browsing mode. Otherwise you can set the disk cache to a low setting like 50 MB via browser.cache.disk.capacity. You can check the current cache usage on the about:cache page.

The network.http.use-cache pref was removed in Firefox 43 because disabling the cache broke things in Firefox.

cor-el said

You should leave the memory cache enabled. Firefox needs some caches in order to work properly. If you want to disable the disk cache then you can consider to use Private Browsing mode. Otherwise you can set the disk cache to a low setting like 50 MB via browser.cache.disk.capacity. You can check the current cache usage on the about:cache page. The network.http.use-cache pref was removed in Firefox 43 because disabling the cache broke things in Firefox.

This is a rubbish suggestion, js etc is still cached in private browsing!!