Duolingo is the world's most downloaded education app, so naturally people are curious about how we do things here! There's a lot of work that goes into making learning free, fun, and effective for learners around the globe. Here are the answers to some of the most common questions about our app and courses. Read on for a behind-the-scenes look at how we think about learning and language teaching!

The most common questions we hear at Duolingo:

Duolingo the owl in front of a chalkboard with illegible writing

Can Duolingo make me fluent?

Research shows that Duolingo is an effective way to learn a language! But the truth is that no single course, app, method, or book can help you reach all your language goals. Instead of measuring "fluency"—a vague goal that language experts and educators shy away from—we assess learners across four domains: speaking, writing, reading, and listening. Learners who completed the beginner content in our Spanish and French courses had reading and listening scores comparable to four semesters of university study! Our learners are also successfully acquiring speaking skills, with about half of learners achieving on-target speaking scores—or better! And we continue to evaluate our teaching methods and effectiveness for learners of all levels.

We also take into account learners' goals and needs at different proficiency levels, using the CEFR, an international language standard, as a guide. We use this combination of language skills and proficiency levels to create a suite of free learning tools; for example, our audio lessons get early learners practicing realistic speaking and listening scenarios, Stories teach learners of all levels reading and listening through conversational dialogues, and our award-winning Duolingo Podcast teaches intermediate learners about culture and spoken language around the world.

Are Duolingo courses developed by real people?

Yes! Our curriculum designers and their teams of content creators include teaching experts, linguists, and native speakers, and many are all three in one! The work of creating a course from scratch includes carefully organizing communication goals for different proficiency levels and then writing thousands of sentences to teach really specific words and grammar in each unit. Our longest courses, like Spanish and French for English speakers, include tens of thousands of phrases and sentences to teach through B2 in the CEFR scale!

We do use artificial intelligence in other ways to improve the learning experience! We pair that classroom expertise with machine learning technology to personalize our lessons. Instead of offering every learner the same course, each Duolingo learner sees exercises in a totally unique order, selected just for them! Our algorithm studies each learner's responses to understand what material they've learned and what is still difficult and then adapts upcoming exercises to maximize effectiveness: the algorithm shows slightly harder exercises for things the learner knows well, and it provides more foundational exercises for topics that are more challenging.

We also use machine learning to help prioritize updates to our courses. This is especially important for managing the 200,000 learner-submitted reports we receive each day—by using technology, we can flag the reports most likely to be translations that we need to add to a course. This is a great way to make the most of our humans' expertise (teaching and language!) with one of machine learning's strengths (processing huge amounts of data).

Why does Duolingo have such weird sentences?

Did you know? All our sentences are written by real people. So why are the sentences a little goofy sometimes? One reason is simply: why not? Duo himself is known for being a little silly, and that attitude has made its way into our courses as well. The people behind the courses are real speakers of the language, and so each course's quirkiness represents the sense of humor of its creators. Plus, quirky sentences can be good for getting you to remember content, because surprising information makes you pay more attention.

When will Duolingo add the language I want to study?

For years, certain Duolingo courses were made and maintained by volunteer contributors, which allowed us to build up our course offering and include many languages and course directions that we would otherwise have been unable to provide. As we've grown and changed, so has our course creation system! Today, new courses are created by paid contractors who work with our curriculum teams. This change means our contractors work more predictable hours on courses, and they work more closely than ever with our teaching experts, from comprehensive onboarding to linguistic workshops. This refined system means we're spending more time thoughtfully evaluating which courses to add and when, as well as what kinds of resources are needed in terms of external teaching and language experts.

In the short term, this means we haven't created as many new courses recently as our learners might remember being introduced years ago! We're putting more resources into assembling and vetting top-notch teams for new languages and into creating new content and learning tools for our existing courses. That can feel frustrating if you've been waiting to learn one of the thousands of languages Duolingo doesn't teach yet (did you know there are over 7,000 languages in the world today?). But we do offer more than 100 courses in over 40 languages, and our efforts to focus and prioritize mean that we’re improving and growing the languages we already teach.

Why does Duolingo teach made-up languages?

There are a lot of reasons why people study constructed languages. Conlangs, or made-up languages, are often associated with fandoms and franchises of movies and books, and studying their fictional language is a way people connect with the lore and with each other. Other conlangs, like Esperanto, were created for social and linguistic reasons; Esperantists, or people who study Esperanto, are some of the most active and passionate conlangers and even raise their children in the language.

Duolingo teaches three conlangs, Esperanto, High Valyrian from Game of Thrones, and Klingon from Star Trek, primarily for one reason: People want to study them! It also helps that these languages don't have to be aligned to the international language proficiency standard that Duolingo uses, the CEFR, so no Duolingo learning and teaching resources are used to create them. (And when it's the language's own creator making the conlang's course, Duolingo also doesn't have to evaluate and ensure their proficiency in the language!)

Instead, conlang courses and campaigns use a small part of Duolingo's marketing and partnership resources because they bring in a wider range of learners to the app, which in turn creates more interest in the natural languages we offer and more opportunities for paid subscribers. This is really important for the company, and more learners and thus subscribers helps support our mission to make (and keep) all our language courses available to everyone for free.

Speaking of… is Duolingo free?

We see this question a lot and the answer is: yes. Duolingo is a free language-learning platform, and every language and lesson is totally free! No matter how much you study with us, whether you're learning one language or dozens, all the content in our courses is free, from the first lesson to the coveted golden owl at the end. We do have a premium version called Super Duolingo that comes with perks like no ads and unlimited hearts, so you can move through lessons faster. The quality of learning tools and language education that you get on Duolingo's free version is just as effective—and fun!—as with the subscription.