I've seen similar extensions for Firefox for years - one or two that replace words on webpages with Mandarin/Japanese translations (and I think even allows you

I've seen similar extensions for Firefox for years - one or two that replace words on webpages with Mandarin/Japanese translations (and I think even allows you to replace only the ones you have on a wordlist - meaning that you can choose to revise words via browsing). I've always meant to use those extensions but never got around to. Guess I won't be using this one since I don't use Chrome (I still find it a surprise to discover that most web developers actually use Chrome and not Firefox).