I have not found Duolingo valuable for learning a language from scratch – my experience with German, in particular, was terrible. Then I tried to do Japanese with it, and trying to use it to learn Japanese from scratch was also terrible.<p>However, after I took a couple of years of real (institutional) coursework in Japanese, and needed to just get a little better at recognizing proper grammar constructions, it actually proved very useful – at the paid level, anyway, where one can "skip"/place into higher levels – and it seems their Japanese module in particular has drastically improved in the last couple of years.<p>So my two cents are that used for language learning alone it's pretty useless. But used as a reminder aide for concepts already learned it can be a good app, especially to just hear how one might phrase a sentence more "naturally" (for a Japanese ear).<p>For Kanji, though, WaniKani is king.