Hi, usually this problem is with links ''outside'' of Firefox, for example, in Microsoft Office applications, Acrobat, etc. Normally, those are governed by your default browser setting, but especially for Outlook, check this article: [[Setting Firefox as the default browser does not work - What to do]]. If there is a problem with links ''inside'' Firefox, are they links to PDFs or other types of content other than regular web pages? You can check whether Edge is specified as the program to use for opening those content types over on the Settings page. See: [[Manage file types and download actions in Firefox]]. Any progress so far?