非常に良いです。
高速。
色彩設計されていない目に痛いサイトを見ることができます。

このアドンを無効にしたり削除したあとも、白黒表示の状態です。元の色に戻りません。

一部レイアウトが崩れるサイトがあります。
例：
http s://kotobank.jp/word/晴れ-1578634

Works perfectly, even with video players. Also compatible with Dark Reader, which is a huge bonus. I normally put a greyscale filter on my phone to stop me from getting too distracted, and the same would work on my PC, but I often need colour for pdf reading. Greyscale Browsing is the easiest solution to this by just dimming out my browser and nothing else :)

Really simple and useful for concentration, also toggles grayscale for all tabs, despite what other people write.

An extension I didn't know I needed! I greyscaled my mobile phone years ago, and this ability to do same "on demand" for the computer browser is... awesome. Helps with readability and lessens eye strain on many otherwise glaring websites. The only request would be a way to toggle it on/off for ALL tabs, instead of per tab.

Works great. Click on, click off. Perfect for what I need

I really appreciate finding this extension. Bravo! Simple, it just works and does all that is needed.
Personally trying the whole mac and mobiles in grayscale, need a quicker switch and here it is on firefox. Would appreciate customizability like colourful domains. Eg, I'd like some websites to be greyscale aside for the largest images, like booking.com, autoscout24.com/ch, comparis etc. Still, thanks for this work shared with all.
For those looking for OSX toggle: there is a script using this code https://apple.stackexchange.com/questions/196761/how-to-toggle-with-grayscale-in-yosemite saved as application and using this page to create a service to call with a keyboard shortcut: https://apple.stackexchange.com/questions/196761/how-to-toggle-with-grayscale-in-yosemite

Reading of websites with weird colors on fonts/background is much easier.

Maybe an enhanced contrast option would even improve readability?