Thus, a quick and dirty approach: First, type about:config into the URL bar. You’ll see a warning, that advises you to be careful. Be careful. After carefully dismissing the warning, enter network.http.use-cache into the filter bar. You should now see the preference of the same name. Double click on the value to change its value. If the value is set to false, the cache is disabled. If the value is set to true, which is the default, the cache is enabled. Despite the name, caching of sites using the https protocol will be disabled, too. And don’t forget to re-enable the cache after you’re done with whatever you wanted to do.