What I believe you may be referring to is Firefox's ability to [https://www.ghacks.net/2019/03/01/firefox-67-automatically-unload-unused-tabs-to-improve-memory/ unload tabs if it's running low on memory]. This is designed to be a performance enhancement, since there's no point in keeping tabs that haven't been accessed in a while open and eating up your computer's resources. The feature is only supposed to trigger when your computer is low on memory, in which case you don't really have a lot to spare. Fortunately, there appears to be a way to disable this feature. Simply do the following: #Type <code>about:config</code> in your Firefox address bar to open the [[Configuration Editor for Firefox|Configuration Editor]]. #Bypass the warning (we'll be careful, I promise). #Find the <code>browser.tabs.unloadOnLowMemory</code> preference. #Double click it to change the value to <code>false</code>. #Restart Firefox. Hope this helps.