Yes, you can learn Indonesian on Duolingo, and the course is more serious than its reputation suggests. Five sections, somewhere around 1,900 words, and it exists at all, which is more than learners of Thai or Tagalog get from the same app.
It will also leave you saying tidak to people who say nggak, and it will never mention that this is happening. That is the real problem, and it is not the one most reviews complain about.
What is actually in the course
The English-to-Indonesian course runs across five sections, from Rookie through to a Daily Refresh section at the end, for about fifty units in total. Independent counts of the course data put the vocabulary at roughly 1,900 words. Learners who have finished it report somewhere between a hundred and a hundred and fifty hours of work, which is three to five months at an hour a day.
Those numbers are worth holding onto, because they are the honest scale of the thing. Nineteen hundred words is a real vocabulary. It is also about a quarter of what you need to follow a conversation between two Indonesians who are not slowing down for you.
The course has no official CEFR level. Duolingo publishes those for some courses and not for Indonesian, so anyone telling you it takes you to B1 is guessing.
What it does well
Word order, drilled until it is automatic. Indonesian sentences are built by putting words next to each other in the order you would guess, and Duolingo’s format is genuinely good at making that reflexive. Saya mau kopi, dia tidak mau kopi, hundreds of times, until you stop assembling it and start saying it.
The absence of grammar you keep expecting. No conjugation to drill, no gender to memorise, no articles to place. The app never has to teach you these things, and after French or Spanish the silence is disorienting for about a week. Then it becomes the reason you are moving so fast.
It puts something in front of you every day. The streak is a psychological trick and it works on most people, including people who know exactly how it works. Fifteen minutes a day for four months beats a grammar book you open twice.
It exists. Duolingo added 148 courses in April 2025 and Thai and Tagalog still are not among them as target languages. If you want a free, structured, gamified course in a Southeast Asian language, Indonesian is one of the few you can have.
The half it never mentions
Here is where it gets uncomfortable, and it is not the complaint you usually read.
Duolingo is not stuck in textbook Indonesian. The course teaches aku and kamu alongside saya and Anda, and its notes even label them as the informal pair. That is more than most beginner courses do, and it is worth saying clearly.
What it does not teach is the word that replaces tidak in almost every real conversation.
What the book says: Saya tidak mau.
What you’ll hear: Aku nggak mau.
Nggak is not slang in the way English speakers imagine slang. It is the default negation across Java and Jakarta, in offices, in text messages, between friends and between strangers of similar age. A course can reasonably decide to teach the standard form first. What it cannot reasonably do is finish without ever telling you the other one exists, and that is where the app leaves you.
The consequence is specific and slightly humiliating. You arrive with four months of daily practice, you produce a correct sentence, and the person in front of you switches to English. Not because you were wrong. Because you sounded like a form. The lesson on tidak against bukan covers the standard rule, and the saya against aku lesson covers the half Duolingo skips.
The affixes turn up, the explanations do not
The course does contain the affix system. Me-, ber-, di-, -an, ke-…-an, me-…-kan, me-…-i all appear in its content, which surprises people who assume Duolingo stops at tourist sentences.
The trouble is that they appear as vocabulary. You meet mengirim and you learn mengirim. Nobody tells you it is kirim with me- attached, that the k has been swallowed, and that the same thing happens to p, t and s. You end up memorising four hundred separate words that are actually forty roots wearing six prefixes.
That is the difference between finishing the course and understanding the language. Six rules cover every case, and they take an afternoon: what the affixes are, then me- in detail. Do that afternoon at any point during your Duolingo months and the app becomes twice as useful, because you start seeing structure where you were seeing flashcards.
Where it stops
Learners consistently report the course thinning out well before the end, with the substantial material finishing around the third section. Whatever the exact shape, the ceiling is the same: you finish able to build correct simple sentences about everyday objects and actions, and unable to follow two Indonesians talking at normal speed.
That is not a scandal. It is what a free general-purpose app can deliver in a language with a hundredth of Spanish’s learner base. It becomes a problem only if nobody tells you, and then you spend month five wondering why the app says you are done and the warung disagrees.
What it gets you in a warung
Concretely, after finishing the course you can order food, ask a price, say where you are from and where you are going, and understand a slow reply. That is a genuinely useful travel level and it is more than most visitors ever reach.
What will still catch you: the particles that carry the tone, sih, dong, kok, lah, none of which the app teaches; the shortened forms people actually use, nggak, udah, gimana; and the speed. Indonesians speak quickly to each other and slow down for foreigners, which means your first real conversation feels like a different language from your last lesson.
Why it makes you feel further along than you are
The exercises that dominate the app are recognition exercises. You are given the words and asked to put them in order, or given four options and asked to pick one. Recognition is much easier than production, and it is not the same skill: you can tap the right tile for belum forty times and still not have the word available when a neighbour asks sudah makan? and waits.
This is why people finish long streaks and freeze in their first real exchange. The app measured whether you could spot the answer. The warung measures whether you can produce one, from nothing, in about two seconds.
The fix costs nothing. Say every sentence out loud before you tap it, and cover the word bank when the exercise offers one. It makes each lesson slower and roughly three times more useful, and it is the single change that separates people who finish Duolingo able to speak from people who finish it able to recognise.
So should you use it
Use it if the streak keeps you practising, and use it knowing three things.
It is a warm-up, not a course. Put an hour of grammar reading next to it early rather than late, so the affixes become a system instead of a word list. And check the register of everything you learn, because the app will not do it for you.
If you want the wider picture, the piece on what each Indonesian resource is actually good for compares the paid apps, the one book worth buying and what a tutor costs. If you are still deciding whether to start at all, the honest answer on how hard Indonesian is is the other half of that decision.
And if you have already done a few Duolingo months, the level test will tell you where that actually put you in about six minutes. It is twenty questions, it is free, and from B1 on it asks which register you are in, which is the question Duolingo never asks.