Affected OSes: Ubuntu/Xubuntu 18.04.1/18.04.2 LTS Non-affected OSes: Windows 10 Browser: Firefox latest stable version and some previous versions at least back to when Ubuntu 18.04.1 was out. Machines: Intel Core i5, desktop PC, either using a GPU card or the integrated one. Asus X553M, notebook Problem: Firefox is very slow when loading a given host for the first time, e.g. www.google.com or www.youtube.com After it's done loading, browsing on that domain is ok. Please watch the video (it's on veoh.com) since it's the best way to understand the problem. https://vimeo.com/319319274 Some text and web pages content are in italian because of the geolocalization. In the video I use VirtualBox for recording convenience but it's the same behaviour in the host machine. Tried: Everything (Ubuntu clean install, reset Firefox profile, proxy settings, disable hardware acceleration, disabling/removing all plugins and extensions, connect to cable - no router). Important: Chromium and Opera work fine. Therefore this is obviously a bug in Firefox. Of course it may only happen under very specific hardware / network combinations, otherwise one thousand people would lament this problem. So I'm open to give additional information. Related bug report link: https://bugzilla.mozilla.org/show_bug.cgi?id=1530205