Here's the about:config info. Apologies in advance for the length, but the names are somewhat opaque so it seems best to lay it out completely. In a new tab, type or paste '''about:config''' and press Enter. Click the button promising to be careful. In the filter box, type or paste '''link.o''' and pause while the list is filtered. Double click these and set the value as desired: '''(A) browser.link.open_newwindow''' 3 = divert new window to a new tab (<u>default</u>) (checked*)<br> '''2 = allow link to open a new window''' (unchecked*)<br> 1 = force new window into same tab '''*''' First checkbox in Options > Tabs '''(B) browser.link.open_newwindow.restriction''' - for links in Firefox tabs 0 = apply the setting under (A) to ALL new windows (even script windows)<br> 2 = apply the setting under (A) to normal windows, but NOT to script windows with features, which will open as new windows (<u>default</u>)<br> 1 = override the setting under (A) and always use new windows '''(C) browser.link.open_newwindow.override.external''' - for links in other programs -1 = apply the setting under (A) to external links (<u>default</u>)<br> 3 = open external links in a <u>new tab</u> in the last active window<br> 2 = open external links in a <u>new window</u><br> 1 = open external links in the <u>last active tab</u> replacing the current page So if you uncheck the box in the tab settings, it should take care of all kinds of links, but you also can set the other preferences to reinforce your preference if the standard approach doesn't seem to be working. ---- Your "More system details" shows the presence of a user.js file, which typically is created by third party software to override your settings at startup. Unless you created the file, you might want to rename or delete it and see whether that helps with Firefox retaining your preferences. This article has the details: [[How to fix preferences that won't save]].