Duolingo is a platform where you can learn many different foreign languages for free. It’s a great way to start learning a language you are interested in and probably the best example of the use of gamification in language learning.
The Duolingo team, sadly, does not publish much statistical data about its user base, so I decided to summarize at least the publicly available figures (from the incubator). The following table shows the total number of users (in millions) for languages that are studied by at least a million users or more. The language codes in the third column indicate languages other than English in which you can learn the given language:
|English||399.72||all available languages|
|Spanish||142.51||PT, FR, DE, RU, ZH|
|French||101.65||ES, PT, DE, IT, AR, RU|
|German||61.28||ES, RU, PT, FR, TR, AR, IT|
|Italian||39.86||ES, FR, PT|
Two things should be noted: First, the numbers do not necessarily correspond to the popularity of the given language because some courses were added much later than others. For example, the Portuguese course for English speakers has been around since 2012 and has a French and Spanish version, while the Russian course was created in 2016 and only had an English version for the most part. Thus, the numbers are not directly comparable.
Second, the number of English learners is probably somewhat inflated by native English speakers who take the English course in another language to practice that language. This approach, commonly referred to as “doing the reverse tree”, is quite common among native and advanced speakers of English.
The point is that Duolingo courses are mostly focused on translating sentences from the target language into the base language (which is usually English). Doing the reverse tree is generally harder and allows users to practice translation into their target language (but it also has some downsides; for instance, the listening exercises become completely useless).