This seems to be the night-mode extension with the smallest file size, and because it's so tiny it's easy to check the code yourself to make sure it's respecting your privacy. (Download the file by right-clicking on Add to Firefox button, choose "save file", then open with an archive extractor like 7-zip).

Doesn't work on my phone - Samsung Galaxy Note 2. All the pages are still white. If anyone knows how to fix it, please let me know.

This add-on for me:
1. Complementary to Dark Reader.
2. Easy to switch on or off. (Plus) There is only a single button in the menu. No option pages.
3. May omit some pictures. (Minus)

While this addon works very well initially, when I navigate to the next chapter on https://tiraas.net/2016/05/30/10-35/ it frequently fails, so I have to disable it and re-enable it. (not every time, but more than half the time I'd say.) It might be something to do with a timeout or a late load of a stylesheet on that page. (I'm on Firefox for Android)

Great consistent colors across all sites! Shame it doesn't work with the vim-vixen addon though.

Appreciate it for working well on Firefox Android. Of course, the plugin satisfies me on FF Desktop. Thnak you!

Just what I was looking for. Simple one click toggle, works well on mobile. The black it makes the background is usually pure black, which looks great on AMOLED phones.

Fails in weird ways on some sites, but it's easy enough to simply turn it back off again on those sites.

simple and efficient

Very nice - even contributed to it , I liked it so well. The only thing I wish it had, is blue text instead of green - just a personal preference of mine. Appreciate all of the creator's efforts.

Unfortunately, the "next" change did not include colors - specifically blue, even tho creator indicated she would. So, I am not using it.

It would be cool to be able to set different color schemes. I really would like to see option with grey out colors instead of so dark intensive! :)

Makes youtube videos so much easier to watch at night. But I wish I could still see the seek bar while it is active, it unfortunately turns opaque.

I was in the process of porting this extension. Ive liked it for a very long time. It simply blacks out most parts of a page, whereas most other extensions usually put a shade of blue or grey, and thats not enough for me.

If there is one criticism I have, it would be the fact that a white blip is shown before the addon can do its magic - as I encountered however, that is probably because of the webextension event infrastructure and not the fault of the addon.

I am sorry to report this add-on works not very well on some sites, for example the popular dutch site https://www.buienradar.nl/.
On the positive, Simple Night Mode provides a button to return to Day Mode really easy and quickly.