Hello, To completely clear Firefox from search settings, you will need to : Change your default search engine Click menu>settings>search>default search engine, then change it to anything but yahoo. Then, you will also need to delete any Yahoo related extensions. Press Ctrl + Shift + A (win) or Cmd + Shift + A (mac) and remove any extension related to Yahoo. Next, if you have a Firefox shortcut and it leads to Yahoo, Right click your shortcut, select properties, then go to the shortcut tab and locate the Target field. If you see any Yahoo.com or related links in the shortcut, it is easiest to delete the shortcut and create a new shortcut for Firefox. If Yahoo persists, you will most likely have to reset Firefox, but make sure to keep a backup of essential Firefox data.