Firefox 54 was released, and with it we finally get multi-process. The old Firefox used a single process to run all the tabs in a browser, and a complex site in one Firefox tab could slow down all the others. That often meant a less than perfect browsing experience. Firefox now uses up to four processes to run web page content across all open tabs. This means that a heavy, complex web page in one tab has a much lower impact on the responsiveness and speed in other tabs. By separating the tabs into separate processes, Firefox makes better use of the hardware on your computer, so it can deliver you more of the web you love, with less waiting. Medium has a nice write-up of the new version of the browser. In order to run multiprocess, your add-ons need to support it as well. You can check compatibility using this plugin.