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How Good Is Duolingo At Teaching Languages?

2023-11-18 13 min read Apps marco

I have been long fond of Duolingo, an app that teaches languages for free. You can use it on the phone, you can use it on a web site, it teaches language in a playful way that people call gamified. You get points, you compete with others, and you get constant positive feedback.

More than just that, Duolingo has a series of courses for less common languages. I am particularly fond of the Esperanto and Hawaiian courses, as I love both languages and because there really wasn’t a good alternative for Duolingo before. Hawaiian, in particular, was taught by the University of Hawaii and the course was a for pay program.

I am back to Duo now, learning French for the third time. I love the French language, I find it strange and weird in just the right ways - what with the nasal consonants that all sound the same, and the hundred letter sentences that boil down to three sounds. The word for now is “maintenant,” which originally means “holding hand;” the word for today is “ajourd’hui” which is newspell for “au jour d’hui,” which means on the day of today.

I went through Duolingo because the course by the Academie Francaise in Denver would have cost hundreds of dollars, which seemed a lot for a place that is meant to foster the learning of French and French culture. There are other apps that do the same as Duo, but I was already familiar with it and knew people actively using it to learn French.

Obviously, having only experience with this one app, I can’t really compare it with others nor form a realistic view of what language learning from an app looks like. I am continuing with it, so I may update this article in an ongoing manner.


The first question in my mind is the most fundamental one: do I speak French better now that I spent 100 days on Duolingo? The answer is an unmistakable, very loud YES! In particular, the three main areas of language learning all have improved dramatically: I can understand written French better because my vocabulary has expanded in areas that are not of interest to me but that are common; I can understand spoken French much better, because Duo focuses strongly on listening exercises; and I can speak much better because Duo forces me to say sentences out loud and its listening engine is pretty good.

I must say, this also took a lot of effort on my part. I generally do about an hour of Duo a day, split in half between morning and evening. You’ll find me after morning coffee on the couch, talking to the phone. And then the same in the evening, trying to get my XPs up (experience points).

The question in my mind is if this is the most efficient way of learning a language, and the answer is another unmistakable no.


As a general overview, Duolingo courses are divided in Sections, who are divided in Units, who are divided in Levels, who are divided in Lessons. This last one is atomic: you pass the whole thing or you fail it.

Within a Lesson, there are different kinds of exercises:

  • Pair matching, where you are asked to match a word in the language you are learning with your own on a grid
  • Speaking, where you are spoken to a sentence that you have to repeat
  • Listening, where you are told a sentence and have to find a matching reply (out of two)
  • Word matching, where you are told a sentence and have to find one word of it out of two possible choices
  • Translating, where you are presented with a sentence in your language or the target language and have to translate it

As a huge aid, Duo offers bubbles most of the time: instead of having to type the entire word, you are presented with a selection of words and you just have to click on the word you want and it is added to your response. That makes translating exercises, but even listening exercises much easier, because you only have a limited selection of possibilities, and because you can’t spell the words wrong.

Lessons come in three types. The most common one is the Material, where you are presented with new stuff. New words, new concepts, new grammar. Then there are Recap sessions, called Personalized Practice. Finally, Stories that are interspersed with the other stuff to break up monotony and give you a more narrative approach to learning.

App or Site?

Duo offers its functionality on both a mobile app and a web site. The functionality is largely interchangeable, but there are notable differences. In particular, the bubble approach doesn’t work very well with a mouse - there is a lot of moving around involved, and the mobile screen is better with instant tapping.

Conversely, no matter what I do, typing words in a foreign language without the aid of autocorrect on a mobile screen is a pain. It’s not made better by the fact that French has lots of extra characters that add to the typing woes. Duo fortunately is lenient with the accents, but the apostrophe is everywhere and on my on-screen keyboard it’s a pain to type, because the long press I would usually use (long C) is taken by the cedille.

The problem with the mobile keyboard is inherent with mobile keyboards in general. After three months with Duo, my accuracy has gotten a lot better, but I still make mistakes on every single sentence I type. I could turn on autocorrect for French, of course, but then I would not learn as much, as I would get suggestions with the correct spelling.

I got myself a Bluetooth keyboard and use that on Lessons that have a lot of typing, usually Recaps. That works a lot better and I suggest you do that, too, if you find that you make too many on-screen errors. I think it’s a shame that Duo only has general typo detection and doesn’t seem to understand that certain typos are just from placing the finger on the wrong spot, not from trying to type the wrong letter.

App Time Issues

Duo is old enough to have been designed as a web site first and the app is only second. It shows in many ways, the most important of which is that there is no offline mode. That is very, very annoying, as you can’t learn a language, not even a little of it, while offline. There is also no option to download lessons that I could find, so learning on a plane or in a tent, when you would have plenty time, is not possible.

That’s not all there is to it. In addition to not being able to learn anything while offline, you are also forced to wait between lessons for download of new material. That could be fixed easily if Duo downloaded (prefetched) a lesson while you are completing another, but someone Duo doesn’t want to do that.

Duo in general loves to make you waste time. This absolutely could be part of the learning experience and it is possible that Duo is doing it very consciously, but it is annoying when you try to get through a lesson and you get an encouragement interstitial. You can disable a lot of the animating, but some of the interstitials when you gain a prize or move up a rung of the ladder are forced upon you.

I guess it’s a little like when you play one of those casual games, think Bejeweled, and a lot of the time is spent watching jewels collapsing with each other. In Duo, there is a lot of encouragment that needs to be clicked to the side to get to the next teaching experience.


There was a recent reorganization of the units, seemingly to better align with international standard of language learning, and it’s been a bit touch and go since. I hope they get the situation under control.

The bugs are numerous. Sometimes, you finish a Lesson and Duo will forget about it. Then you have to repeat the same thing again, which is slightly annoying. Other times, the app will hang at the end of a Lesson. Most of the time it wakes up after a while, but sometimes you have to kill it. It’s about a 50-50 chance whether it will have recorded the progress or not.

Particularly problematic are both the written and spoken engines. You can get into a situation where the app complains about spelling mistakes in the bubbles, where you are absolutely not spelling anything and just choosing words it presented to you. And clearly the app uses computer-generated voice, because sometimes it pronounces words plain and simple wrong. In French, for instance, the word “y” means “there,” while the letter Y is pronounced “i-grek” or “Greek I.” More often than I’d like, the computer-generated voice decides to pronounce the word “y” as the letter, which is (1) wrong, (2) confusing, and (3) a clear sign nobody did a whole lot of debugging.



I don’t know if it’s an issue of boredom, but Duo sometimes falls into these cognitive holes. It will harp on a particular word for no particular reason and repeat it over and over even if you have clearly demonstrated that you know it. One example that makes sort of sense is la chouette, the French word for owl. It’s repeated throughout the course because the symbol of Duo is an owl. Alright, marketing.

But Duo went on forever about the watermelon, la pasteque for no reason. I am not a watermelon hater, but it strikes me as odd that I would know that word because Duo was merciless presenting it to me, but I am much foggier about the words for other fruits and vegetables. Still don’t know how to say artichoke, for instance.

Awkward Phrasing

Another odd quirk of Duo is the weird sentences you encounter. They can be weird for different reasons: Sometimes, the sentences itself is strange, which has been proven to be a good way to make it memorable. Duo obsesses over dreams of dinosaurs for good reason - you remember those phrases.

Other times, the problem is that the sentence is awkward. That’s particularly a problem in translating, as Duo sometimes decides to translate in a weird fashion. For instance, a cle USB is consistently called a “flash drive,” despite the fact that a flash drive is also called a USB drive in English.

Confirming Nothing

Whenever you complete an exercise, you press on a button that moves on to the confirmation screen. Here you have to press once again to move on to the next exercise. The problem here is that when you are just getting a confirmation, the extra click is just time wasted.

It would be probably better if Duo skipped this confirmation step, but stopped if you made a mistake. In general, it would be better if Duo had a “Back” button that allows you to see what happened on the screen before, but for sure it would be better if errors were emphasized more.


Throughout the course, you can get hints when translating a sentence. Words will be faintly underlined and if you click on them, a set of potential translations will appear.

While a great feature, the problem with Duolingo hints is that they are frequently plain wrong. That is, the hint will use a word form that is not accepted by the app.

Duo is very particular about word forms. It teaches you that a teacher is a “prof” or a “professeur,” but it will frequently only allow one of the two options, without explaining why you should use one and not the other. The same is true for thing, either “truc,” “chose,” or “objet.” It happens frequently that you use one of the three but Duo wants another, and you are left without clue. That happens with hints a lot, too.

The opposite issue with hints is that they reveal too much. For instance, they will usually have exactly the right form to use in the sentence, when figuring out which one it is is the main goal of the exercise.


Definitely something that is opinable is Duo’s approach to grammar, which is very post facto. I know there is strong debate over whether to teach patterns or to prefer grammar. Pattern teaching shows you sentences and you learn the grammar by pattern matching (Duo’s preferred approach). Grammar teaching presents you with rules and exceptions, making for a lot of learning before using.

For my taste, Duo errs on the side of too much template matching. There are occasional grammar lessons, but they are very short and contain a lot of “usually” and “normally,” without telling you when things are not either of those two. That’s particularly difficult with verb forms, because French has a lot of them and most of them sound too similar to tell accurately apart. This is a general problem of French, though: a lot of words sound exactly the same and are spelled completely differently.

The Game

Duo tries to hook you into language learning by adding gaming aspects to the app. You earn points by completing Lessons. The points come in two varieties: XP or experience points, that pit you against other “players”/ learners. And what used to be called lingots, that are a sort of rather useless in-game currency.

The main game aspect is to gain more experience points than other people. You are thrown into a “League” with a bunch of other random people, and you can move up or down depending on how industrious or lazy you are. Unlike in “real” gaming, you have no real way to work with or interact with other members of your league. All you can do is “friend” them, in which case they are notified of your “successes” and you of theirs, and you can send each other kudos. You are absolutely never allowed to interact directly.

It seems that Duo has had issues with inter-league abuse, because they have taken away a lot of the interpersonal functionality. For instance, you used to be able to use a photo as avatar, but now you can only use and approved symbol. I guess at some point there was more interactivity with other learners and that was taken away because that’s why we can’t have nice things.

Aside from the XP and the currency, you can also earn badges for various things. The most important thing in Duo is your Streak, or number of days you used the app without interruption. Duo is obsessed with it and the only useful thing you can buy with the in-game currency is a Streak Freeze, or ability to continue the Streak even if you had a day without.


Duo is freemium: you can do a full course for free, but you can pay to get some “advanced features”. Interestingly, the premium version doesn’t teach anything the free version doesn’t. The differences are all in small things: you don’t get ads, you can buy your way out of issues (like you get automatic streak freezes).

You absolutely can complete a course in Duolingo without paying. The thing is, the annoyances with the free version are sufficient, you should pay for the premium version if you are serious about learning a language. You are going to spend hundreds of hours on this app, and it makes you waste time on the best of days. It’s worth to upgrade just to save the tens of minutes it costs to go through the forced delays.

Duo premium is also not expensive compared to other forms of language learning. Sure, it is comparable to other online subscriptions, but a “real” language course is a factor more expensive, much less convenient, and nets you the same in the end.