Most consistently working reverse-image search I've found, with the small caveat that it halts on the new-tab google main page for the 1~ second it takes to load, which feels weird every time, looking as if it didn't work. But it does, a second later, every time.

I've waited a long time. I am happy when i found this extension. Thank you very much. You are a GREAT developer!

これのおかげでchromeで出来た画像検索がfirefoxでも出来ます。ありがたいです。

This works perfectly. And it allows to set search results in current/foreground/background new tabs. Very nice!