Truly impressed by how good the sites I use now looks after dark. Being a web developer, I can assure you that creating a nice looking dark theme is no easy task. That dark reader is able to fix websites which were designed for light mode only, is very impressive. I tweaked the brightness and sepia settings to my preferences. You should take some time to do that too. And if you appreciate the extension, consider supporting the developers. It's optional but encouraging. Five stars!

don't work

They want 10€ just after installation. Avoid.

best

while I enjoy dark reader, it makes websites look a lot better, but dark reader slows Firefox on Android to a crawl, I just cannot take it, and after reading an Reddit post where users were complaining about the sluggishness of Firefox on Android, a user mentioned dark reader being the culprit, so I disabled dark reader.
Problem solved, sorry, not sorry

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This add-on makes websites less painful at night.

Godsend extension, saved my eyes! Lot's of features & benefits.