Not Duolingo, but has advantages
Mondly is an app that basically attempts to mesh the gamified language approach of Duolingo with the conversational emphasis of Rosetta Stone. Since I am an avid Duolingo fan and have completed 5 language trees, my curiosity was piqued with Mondly. What does this app do differently from Duolingo that justifies charging money? So I tried it out to supplement my Persian studies in grad school and to refresh my Japanese, and... I honestly wasnt all that impressed.
One of the best things about Duolingo is that the courses are built from the ground up by native/fluent speakers who understand how to learn the language. Mondly seems to take a more phrase book approach, translating stock phrases into the target language for users to translate again.
This leads to situations like learning the word "Kare" for he/she as one of the first Japanese words. In my two years of formal Japanese study, I was never taught this word, because no one uses it. Another example is the frequent use of "to" for "you" in the Persian course. Persian learners: NEVER use "to" with anyone you dont know really well, as it is considered particularly rude. Always make sure to use "shoma".
The other problem with the phrase book approach is that it teaches memorization rather than cognition. Duolingo is great at introducing the building blocks of grammar for new learners. Mondly leaves this subject until the last screen, and the app suffers for it in my view.
That said, the addition of daily lessons is a good idea that I think Duolingo could take some cues from (although it would be an extra burden on the volunteer creators), and if youre a hipster like me who cant stick to the Romance languages like everyone else, Mondly has many options that Duolingo doesnt have.
But bottom line: I would say that if Duolingo has the language youre trying to learn, use that instead.
HardRockGuru about
Mondly: Learn 33 Languages, v5.0