Paralelo vs Duolingo

Paralelo or Duolingo: the short answer

Written by Paralelo's founder: we make one of the two apps compared here. The research cited below is linked, so you can check it rather than take our word for it.

If you are starting a language from zero and want a gentle daily routine, start with Duolingo. If you already know some of the language, or want to spend your time reading real literature rather than exercises, Paralelo is built for that. They are different tools, and many learners will get the most from using both.

The rest of this page explains why, without pretending either app does something it does not. Duolingo is a course: it decides what you learn next. Paralelo is a library and a reader: you choose a book, and it helps you understand it.

What is Paralelo?

Paralelo is a reading app for learning languages. You read a public-domain classic in its original language with a translation beside it, and the two columns are aligned phrase by phrase: hover a group of words on a computer, or tap it on a phone, and its counterpart lights up in the other column. It works in the browser.

The library is books only: classics from Project Gutenberg, with originals in English, French, Spanish and German, and translations into English, French, Spanish, German and Portuguese depending on the title. There are no articles, no audio, no flashcards, no exercises and no streaks, and you cannot import your own texts.

Two features do the teaching. The alignment lets you check any phrase without leaving the page or losing your place. And when a whole sentence resists you, you can select it and ask for an explanation: what it says, what it means, one grammar point and any cultural note the line depends on. Your reading position is saved across devices, and switching the translation language keeps your place.

The translations are machine translations made by a language model, and every page says so. Before a translation is published it passes automatic checks (every paragraph present, plausible lengths, the right language, consistent names and numbers, enough words aligned, a sample that reads as natural prose), and then a person reads a sample beside the original.

What is Duolingo?

Duolingo is a course app built around short, gamified lessons: translating sentences, matching words, listening and repeating, a few minutes at a time. Streaks, points and leagues are there to bring you back every day. It covers many languages, has native iOS and Android apps, and is free to use with ads.

Its strength is structure. You never have to decide what to study next, the first lessons assume nothing, and the daily nudge is effective at turning good intentions into a habit. It also practises things Paralelo does not touch at all, such as listening and speaking exercises. Duolingo Stories add short narratives written for learners at each stage of the course.

Its limit is the same structure. The sentences are written for the course, so the language you meet is controlled and simplified by design. That is exactly right at the start and becomes a ceiling later, when what you need is a large volume of real text.

How the two methods differ

Duolingo teaches language in small, sequenced steps and tests you on each one. Paralelo gives you long, real text and makes it understandable. One is practice with feedback; the other is input with support. Neither replaces the other: exercises are good at introducing patterns, and reading is good at meeting them thousands of times in context.

• Who chooses the material: Duolingo's curriculum decides; on Paralelo you pick a book.
• What the language looks like: sentences written for learners on Duolingo; the author's own sentences on Paralelo, idioms, old-fashioned turns and all.
• How you get unstuck: Duolingo corrects your answer; Paralelo shows you the matching phrase in the translation, and explains a sentence if you ask.
• What a session looks like: a few minutes of exercises; or a chapter, a poem, a short story, for as long as you want to read.

If you want the longer case for side-by-side reading, and its known pitfalls (above all, reading only the translation), our guide to bilingual books and parallel text covers it in detail.

What the research says

Both approaches have evidence behind them, and neither has evidence for everything. Duolingo's own published study found that learners who completed its beginning Spanish or French courses read at a level comparable to four semesters of university study. Research on reading shows that large amounts of it build vocabulary and comprehension, provided the text is understandable.

On Duolingo, the best source is Jiang, Rollinson, Plonsky, Gustafson and Pajak (2021), published in Foreign Language Annals and co-authored by Duolingo's researchers. They tested 225 adults in the United States who had used only Duolingo to complete the beginning level of Spanish or French. On the ACTFL scale they reached Intermediate Low in reading and Novice High in listening, scores comparable with university students at the end of their fourth semester. That is a real result, and it is also a measure of the beginning level, not of fluency.

On reading, three studies are cited again and again. Hu and Nation (2000), in Reading in a Foreign Language, found that unassisted reading for pleasure needs about 98% of the words in a text to be known. Nation (2006), in the Canadian Modern Language Review, estimated that reaching 98% coverage of written English takes a vocabulary of 8,000 to 9,000 word families. And Nakanishi (2015), a meta-analysis in TESOL Quarterly of 34 studies and 3,942 participants, found that extensive reading improved reading proficiency, with a medium effect against control groups.

Read together, those numbers explain both the promise and the problem. Reading a lot works, but a learner with a few thousand words is nowhere near 98% coverage of an unabridged novel, so unassisted reading of real books stays out of reach for years. A parallel text is one way to close the gap: the translation supplies the words you are missing, so the reading is assisted rather than unassisted. To be precise about the evidence, the studies above did not test parallel texts, and none of them tested Paralelo. They describe why comprehensible reading matters; they do not prove any particular app.

Which one fits your level?

Duolingo suits a complete beginner best, because it assumes nothing. Paralelo has no minimum level, but what you can enjoy on it depends on what you already know: a beginner can read a three-minute poem with the translation beside it, while a long novel is much easier with some grounding in grammar and everyday vocabulary.

Paralelo does not label its books with CEFR levels, and we would rather not guess. What we can tell you is length and form. José Rizal's poem My Last Farewell takes about three minutes to read. Charlotte Perkins Gilman's The Yellow Wallpaper takes about 28 minutes and is written in short, plain sentences. The Adventures of Sherlock Holmes, at around eight hours, is another matter, though it comes in self-contained stories.

So a beginner can open Paralelo on day one, lean on the translation heavily and still get something from it. But if you know almost nothing, you will be reading the translation and glancing at the original, and a structured course will move you faster at that stage. Once you can follow simple sentences, the balance tips: short texts become manageable, and each book you finish makes the next one easier. If you are weighing simplified books against real ones for that middle stage, see graded readers vs bilingual books.

What each one costs

Both are free to start. On Paralelo, a passage from every book can be read without an account, and a free account opens every book in full. Plus costs €6.99 a month or €59 a year and only lifts the daily cap on explanations. Duolingo is free with ads, and its paid plan, Super Duolingo, removes them.

The difference is what the free tier leaves out. On Paralelo, nothing about reading is paid: every book, every page, the alignment, and five sentence explanations a day. Plus raises that to unlimited explanations, with a fair-use ceiling of 300 a day. On Duolingo, the free tier gives you the courses with ads and some limits, and Super Duolingo adds an ad-free experience and extra features. Duolingo's prices vary by country and platform, so check them in the app.

How to use both together

Use Duolingo for the daily habit and the foundations, and Paralelo for reading volume. A practical split is a few minutes of lessons most days, plus one or two longer reading sessions a week, starting with short texts and moving to longer books as the translation column becomes something you check rather than something you read.

1. In the first weeks, keep Duolingo as your main tool, and read a very short text on Paralelo once a week, such as a poem, to see real language early.
2. When simple sentences stop being a struggle, read one short story or novella from start to finish, looking at the translation only when a phrase blocks you.
3. Use explanations sparingly, on the sentences that stop you twice. Five a day is plenty for most reading sessions.
4. When your Duolingo lessons start to feel easy, shift the balance: more time on books, less on exercises.

Our pages for learning Spanish, French and German list every book we carry in each language.

Start with these three books

Three classics, one per language, each readable in full with a free account. For Spanish, José Rizal's My Last Farewell is a poem of about three minutes, written the night before his execution in 1896.

My Last Farewell

José Rizal · 3 min · Spanish with the translation beside it

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For German, Franz Kafka's The Metamorphosis takes about an hour and a half, and its prose is famously plain for such a strange story.

The Metamorphosis

Franz Kafka · 88 min · German with the translation beside it

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For French, Guy de Maupassant's Boule de Suif is a longer novella, around two and three-quarter hours, and a good next step once short texts feel comfortable.

Ball of Fat

Guy de Maupassant · 164 min · French with the translation beside it

Read free

Paralelo is made in France by Arthur Renaud; you can read more about the project.

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