> Firefox doesn't revert you to defaults

You mean besides that time Firefox reverted everyone's search engine to Yahoo?

It only switched your search engine if you'd never changed from the original default (Google). If you had ever switched the search box to use a different engine, FF continued to respect that.

But why would I change it if I wanted Google, which incidentally is, I'm sure, what most people want? Leaving the default can be as much a choice as changing it.

(I'm on Mozilla's side in this discussion, but that particular move was terrible, even if not too consequential, in my opinion.)

Not changing from the default is as much a choice as changing to something else. They shouldn't have changed it for updates, but for new installs.

Unless you do the "refresh firefox" thing that shows up every time you have 5 addons installed.

The above experience is on the developer edition of firefox, as I haven't tried it on the normal stable release.

I had to deal with friends that were suddenly on yahoo and they didn't know why. So for a lot of people it was swapped out even if it was an accident.

I think Firefox sets itself as the default when you upgrade it and choose default settings.

I meant the search engine thing.

It's pretty normal for a program installer to set itself to handle files.

So then what's wrong when an OS does it?

The OS does set itself to do OS things.

OS shouldn't set your browser.

It's one of the option during the first experience configuration of Windows 10. If you had another browser installed, one of the toggle is : do you want to use Edge as default browser. Hopefully, people that feel that strongly about their browser choice don't just use "Express settings" when installing a whole operating system.

The OS update installs a new browser, which then sets itself as default.

Windows isn't installed automatically.

Let me lay out the analogy more explicitly. I install Firefox, and specifically choose for it not to be my default. I later download an updated version and choose default settings in the installation. Firefox then sets itself as the default browser; it overwrites my previous choice in favor of the default.

I install Windows. I specifically don't set explorer as the default. I install an updated version of Windows and choose default settings. Windows overrides my previous choice.

Right, neither should be doing that in the case of an update. Firefox when updated in the normal manner doesn't make itself the primary browser. Windows 10 is behaving badly.

Firefox will only change things if you specifically get a Firefox installer, where it thinking that's your intent is understandable.