Fantastic extension, highly customizable. It got a slew of bad reviews recently due to a Firefox browser bug, and users not bothering to check the extension's settings before complaining that it doesn't have such-and-such feature, but for anyone who's allowed to use the internet without parental permission it's a wonderful, capable addon maintained for free by a team of very patient, responsive *volunteer* developers (and to be clear, I'm not one of them! But they've given me great help tinkering with dark themes, and I hope one day I'm proficient enough at coding to contribute to the project myself!)