In the advent of forced updates being shoved down our throats due to some addons becoming unavailable and websites supporting legacy browsers more and more, this is a very similar alternative to the old, now outdated Rikaichan.
It gets the job done well enough and uses the same key bindings for the ones it has in common.

However, it lacks in quality of life compared to its predecessor.
There doesn't appear to be a way to change the font size with the text appearing a bit more bloated (and spaced) than I'd like, it removed the ability to put the frames in set corners on the screen using the "a" hotkey (I never used this personally, but was aware of it), and it doesn't allow you to change the order you "shift" through (always being word definition, kanji breakdown, names dictionary) like you could on Rikaichan.

The worst part would be that when switching to the names dictionary for Japanese, when there's so many options to fit on screen it will just make one super long column stretching off the screen instead of splitting it into two columns, effectively making half the options unreadable without zooming the page out by a good chunk.

In the end the important part is that if it works, though, which it does.

C'est super !
Merci beaucoup pour votre travail !!

Next best thing to rikaichan. If only it didn't alter/move the original Japanese text, it would be - dare I say - better than rikaichan. Regardless, it's better than nothing. Although finicky, it does work!

Thank you very much for taking the time to port it to Quantum, Brian Birtles. Much appreciated!

Great

This works exactly like Rikaichan used to work. Excellent! Is there a way to make this work with the new Thunderbird? I've added by the icon does not show. Not sure this is an issue related to Thunderbird beta...

Very well done! Thank you!

Very fast and intuitive to use, and does not behave like AIDS.
One feature I'd like to see is the ability to add different libraries to it. I'll bump this review to a 5-stair if this is implemented, but for now I'll have to go back to Rikaisama

Works very well. I'll give it another star or two when it a look-up bar is added. I might also give it another star if it adds the option to access the preferences without navigating to them through the add-ons page; or if other languages are added.

It would also be nice if the colour of the active "理" button for the black-purple-green colour scheme was consistent with the others (that is, having the character "理" be the same colour as kanji are in the popup — in this case, purple).

This is fantastic. I downloaded it and it worked instantly. No drama. I just wish it had some more functions like save etc. Well, especially save, so that I can make word lists. Thanks to whomever made this.

Very much like the original, and great for that. Missing one thing: a button (or option) that moves the pane to different sides of the screen. Because directly below the word gets troublesome when you're trying to read something that has tooltips.

Another problem I've noticed after use is that: it stops working after Firefox has been open for a while (I don't know what triggers it); and the problem is fixed when Firefox is restarted.

Seems to work fine as long as you manually turn off the "Highlight matched text" option. The option is on by default, and until you turn it off, the addon will often randomly scroll through the contents of text entry fields, and shortcut keys (e.g. to switch dictionaries or definitions) don't work properly there. Cost me several hours of frustration over the course of a month until I found out that option was causing all the trouble.

Hey, great extension, appreciate the work. One thing though, could you add a search function like the lookup bar Rikai-chan had w/ a keyboard hotkey to activate it? That would really make this add-on 5 stars.

Works fine

Rikaichan was the only extension I missed from old Firefox. Not anymore.

Thanks for porting it!

In old version. it have my language (Thai) but it good than nothing. I'm happy to use this add on now. Thank you very much.

Great. Would love EPWING support but other than that it's perfect.