4.9.99 destroys Firefox more than it does good despite the tips cited below. I went back to 4.9.98 and everything is back to normal. You need to review your copy.

The best dark reader extension available - outstanding work! Ignore the recent 1-star reviews about Reddit's website - the bug was introduced by a recent update by Reddit itself, and the Dark Reader developers quickly worked to address the issue.
If you're a (long-time) user of this incredible tool, please consider supporting the developers through a donation to help them continue their fantastic work. It's discouraging (and counterproductive) to see users who have benefited from Dark Reader for years suddenly leaving negative reviews at the first sign of a problem, instead of reaching out to the developers or checking for updates first.

This is one of the most vital and effective add-ons I've ever installed. Not every website/browser/etc has a consistent dark mode, and none handle it as well as Dark Reader. Needing to constantly research, this add-on saves my eyes at night. Even with recent changes to FireFox which temporarily hampered performance, Dark Reader quickly pushed an update and is straightforward about addressing issues. Honestly, this is probably one of the best add-ons next to an ad-blocker out there.

This extension is a huge difference maker for me, and for so many people, reducing eyestrain and promoting eye health. The internet is always changing and squashing bugs is a constant battle. So thank you Dark Reader for your hard work!!!
I want to contribute some encouragement and I will contribute cash as soon as I'm able.
Edit: For users who may need to disable this on a specific website: First, go to the website where you're having issues, then open the extension menu (you should see only your active extensions). Select Dark Reader, then uncheck "Enabled for current website". The menus are different between desktop & mobile, but it's fairly easy to figure out.

really a must-have addon if you don't want your retinas to be burnt to a crisp on a daily basis. i'm rating it 4/5 because it has helped me for so long, but sadly the past days its been having issues with youtube to the point where i can't have it activated at all for it.
every time i try and activate it and refresh youtube homepage, the browser is about to crash and it asks me to stop this addon specifically. when i pause the addon, it works fine and i can refresh youtube without the browser almost collapsing.
were this to be fixed, then its an easy 5/5 for me.

Not works on Mozilla.org page. All other perfect

Thanks Dark Reader team for taking care of our eyes.

To those with v4.9.97 breaking Firefox: Just realized that the Developer's note applies to Settings on DarkReader, not Firefox. Go to the DR icon on the top of your window and choose "MORE". It is to the right of "Filter". Then choose "Default" below.

It was relatively good until today, when it was automatically updated, and now I cannot see the bookmarks in the bookmarks sidebar, nor the menu bar. All is just black, except for the icons for the bookmarks in the sidebar. It became useless. And your answer to Tikitaki makes no sense, as there is no "custom browser theme" option to be disabled in the "General" settings.
PS: I figured it out. I thought that in your response to Tikitaki, you were talking about the Settings in Firefox, when you were talking about those of Dark Reader itself.
So here is how it should be explained:

Open the settings of the Dark Reader > Click the "More" tab > Click "All Settings" > Click/toggle "Change Browser Theme" so that it says "Default browser theme is active".

If you want some custom browser theme, install it or enable it AFTER all this procedure through Firefox Themes settings. You actually may need to uninstall and reinstall the Dark Reader extension and revert to the default Firefox browser theme in the Firefox settings before all this.

I will leave the one star because of the inadequate explanation you gave, and also because you didn't make it work as it should immediately.

With last update I got blank black window and menus in firefox

This extension used to be amazing. Now, it completely breaks Firefox and Firefox even tells me that the extension is slowing down my browser. It makes websites completely unusable. Please fix this. I loved this extension when it worked properly.

It slows down Firefox now. So sad

Something's broken with this addon, it used to work perfectly, now it's slowing down Firefox.
Please fix!

used for a long time, has had performance issues over its lifespan but for ~month or so the performance is horrendous. causes most big-name websites (reddit, youtube, google) to completely seize up and load extremely slow, currently making this add-on completely unusable. i will edit the review if this gets fixed but currently this just straight up breaks your browser

In terms of aesthetics, the best dark mode add-on. But it slows down the browser very much, so use with caution.

Good... almost. For instance, it doesn't work in this very page page at addons.mozilla.org

Slows Firefox to a complete stall. Can't use it anymore. Shame.

Websites load slower than far too slow. And after updates performance seems to even get worse over time instead of better. This add-on is 110% unusable.

changing to 4* after update, will go to 5 once it is functioning correctly. thanks for the update

Was pretty good up until recently where it started causing FF performance to tank.