I've read several forum threads on this and none have a satisfactory answer for this situation though some of the questions were more or less identical to my problem. After a recent FF update (it might have been the previous update but I'm now now at 58.0.1 64-bit), I decided to switch back to Firefox (from Chrome) to make it my default browser. I was running Waterfox (it was based on FF and was 64 bit long before FF went 64 bit), and that was in the list of choices in settings/ default browsers (see the attached image for the window I'm referring to--one is from Mozilla help files and the other that doesn't show FF as an option is the one I am seeing), in Windows 10, the place you're taken to when you choose from within FF to make it your default browser. Edge, IE, Chrome, Opera, and a few others are offered as choices but not Firefox. Waterfox was available until i uninstalled it with the hope that it was causing the problem. I decided against using Waterfox since recently, after an update, it cleared all of my NoScript settings, so I had to start whitelisting all of the good sites again. So now I'm thinking of reinstalling Waterfox and getting rid of NoScript since that was my only issue with it. at least it showed up in the list of browsers to choose a default from. I would stick with Chrome but I don't like the look and feel of it and I certainly don't like it's bookmarking arrangement. Has anyone else seen this behavior where when you click "make FF my default browser" and you're taken to the settings window (Windows 10) that other browsers are listed but not FF? If so, were you able to fix this, and if so, how? I believe there are work-arounds like using default program file settings for launching HTML files, but that's only a partial fix. I want to get FF to display in the default browsers selection window. I believe something is blocking that from happening. I did try a fresh install to refresh everything and that didn't work, either. I don't need advice on the normal procedure on how to make a browser my default one, as I can change to Opera, Edge, etc, at will. I just don't have FF as an option in the list in the settings/default browsers window. Thanks in advance, too. I've been a FF promoter for many years (except for a brief time when I switched to Waterfox, which is based on FF).