Hi Alanaf, I do not use MS Windows Excel. Sorry this is only guesswork, but no one else has answered so I may as well give it a try. I do not know whether Firefox is able to open Excel docs on a local file. Possibly in earlier Firefox versions it may have been possible to view an excel file if you had a suitable plugin. I doubt you would have been able to edit the files in Firefox. MS may well have online services you could subscribe to to do that. (Is it a case of the service is free but you subscribe and pay for the software licence not too sure how it works. I use free Libre Office across Linux & Windows, and even to some extent on Android) Maybe that is what you are trying to do. If so then you should try MS support for answers.