Glossa is a web-based language learning app that lets you upload your own PDFs and EPUBs and read them in 18 languages with click-to-translate, audio narration, and built-in spaced-repetition vocabulary practice. It turns any book you already want to read into a graded reader for the language you are learning.

What languages does Glossa support?

Glossa supports 18 languages: English, Spanish, French, German, Italian, Portuguese, Dutch, Swedish, Norwegian, Danish, Polish, Russian, Turkish, Arabic, Chinese (Simplified), Japanese, Korean, and Hindi. Coverage depends on available CEFR data; languages without curated CEFR lists fall back to a machine-learning difficulty classifier.

What file formats can I upload?

PDF and EPUB, up to 100 MB per file. Books upload directly from your browser to Azure Blob Storage via a short-lived signed URL — the application server never sees the raw bytes in transit.

Yes. The free tier includes 2 books and 10 distinct pages of reading, with every feature unlocked (translation, audio narration, vocabulary games). Pro is $14.99 per month or a one-time $4.99 7-day pass, and removes the book and page limits.

What is included in Pro?

Unlimited books, unlimited pages, AI-generated chapter summaries, and faster book processing. Pro removes limits rather than gating features — translation, audio narration, and vocabulary practice are also fully available on the free plan.

Does Glossa work on mobile?

Yes, Glossa runs in any modern mobile browser. There is no native iOS or Android app yet; the responsive web app is the only way to use Glossa on phones today.

Is my uploaded content private?

Yes. Uploaded books are stored in a private Azure Blob container accessible only to your account, are never shared with other users, and are never used to train AI models. We do not sell user data.

What is CEFR scoring and how does Glossa use it?

CEFR is the Common European Framework of Reference for Languages, a six-level scale from A1 (absolute beginner) to C2 (near-native). Glossa scores every word in your book on this scale and a difficulty slider in the reader controls which words get translated inline — lower slider shows more glosses for harder words, higher slider shows fewer glosses and more original text.

How does the spaced-repetition vocabulary practice work?

Words you tap while reading are saved to your vocabulary list. Glossa surfaces them in short games — matching, fill-in-the-blank, multiple choice, parts-of-speech tagging, and sentence-scramble — scheduled so you re-encounter each word at increasing intervals based on how confidently you answered last time.

How is Glossa different from Duolingo?

Duolingo teaches with a fixed curriculum of synthetic exercises. Glossa is a reader — you upload real books you actually want to read, and translation and vocabulary practice are built around that content. Duolingo suits absolute beginners; Glossa suits learners who can read elementary sentences and want to engage with longer material.

How is Glossa different from LingQ?

LingQ has a built-in catalog of curated lessons and a learner community. Glossa lets you upload any PDF or EPUB and adds CEFR-adaptive interlinear translation, which LingQ does not offer. LingQ has more pre-curated content; Glossa gives you more control over what you read.

How is Glossa different from Readlang?

Readlang is primarily a browser extension for translating words in web articles. Glossa is book-centric — built around uploading PDFs and EPUBs, with audio narration, CEFR-adaptive glossing, and structured vocabulary games. Choose Readlang for web articles; choose Glossa for full books.

Can I import books from Project Gutenberg?

Yes. Glossa has a built-in browser for the Project Gutenberg catalog of public-domain titles. Pick a book in your target language and it imports in seconds without leaving the app.

What voices does Glossa use for audio narration?

Azure Neural Text-to-Speech voices, native-speaker quality in each supported language. Every user gets a default voice per language; additional voices can be unlocked using Glossa Points earned through reading.

Best apps to read books in a foreign language (2026)

Prices and features checked July 2026. Full disclosure: Glossa is our app — it’s in the list, first, with its limits stated plainly. Everything else here is judged on the same criteria.

Reading real books is one of the most effective ways to grow in a language — but only if the lookup friction stays low enough that you keep reading. That is the whole job of the apps below. This comparison covers reading apps, not course apps: everything here puts a book (ideally your book) on screen and helps you through it.

How we judged

Own-book import — can you read the EPUB or PDF you actually want to read, or only a curated library?
Translation display — tap-to-translate (interrupts flow), side-by-side parallel text (splits attention), or interlinear glosses (help under the line, flow preserved).
Audio, vocabulary review, platforms, price.

Quick picks

Adaptive help under the words, in your own books: Glossa
Biggest all-media ecosystem (video, podcasts, books): LingQ
Cheapest solid web reader: Readlang
Native mobile reader with offline TTS: Smart Book or Linga
Curated bilingual stories with narration: Beelinguapp
Netflix and YouTube rather than books: Language Reactor
Free and self-hosted: LWT or LinguaCafe

At a glance

App	Own books	Translation display	Audio	SRS	Platforms	Price
Glossa	EPUB, PDF	Adaptive interlinear glosses	Neural TTS	Yes	Web	Free / $14.99/mo or $4.99 pass
LingQ	EPUB, PDF, web, video	Tap-to-translate, word status	TTS + audio	Yes	Web, iOS, Android	Trial / $14.99/mo
Readlang	EPUB, TXT, web	Tap-to-translate	TTS	Yes	Web	Free / $6/mo
Smart Book	EPUB, FB2, TXT	Side-by-side parallel	TTS	Yes + Anki export	iOS, Android, Mac	Free / $1.99/mo or $24.99 once
Linga	EPUB, PDF, MOBI, FB2, TXT	Tap-to-translate	Offline TTS	Yes	iOS, Android, Mac	Free / $5.49/mo
Beelinguapp	No — curated only	Side-by-side bilingual	Narrated audiobooks	Flashcards	iOS, Android	Free / ~$7/mo
Kindle	EPUB, PDF, DOCX	Tap dictionary / translation	Limited	No	E-ink, iOS, Android, Web	Apps free; books paid
Language Reactor	Text paste; no EPUB	Dual subtitles / text MT	TTS	Flashcards	Chrome desktop	Free / ~$6/mo
LWT / LinguaCafe	TXT / EPUB	Tap-to-translate	No	Yes	Self-hosted	Free

1. Glossa — adaptive interlinear reading (ours)

Glossa is built around one idea: translations belong under the words you don’t know, and nowhere else. Upload an EPUB or PDF (or pick from the built-in Project Gutenberg browser) and the reader shows small glosses beneath the words you’re likely to struggle with at your level — adapting as your vocabulary grows, so a B1 reader and a B2 reader see different pages of the same book. Sentence translation, neural text-to-speech on any sentence, and vocabulary practice built from the words you actually looked up round it out. Free covers 2 books and 10 pages; Pro is $14.99/month or a one-time $4.99 7-day pass.

Here is the display style, live — it’s easier to show than describe:

EnInunalugarplacedeoflatheMancha,Mancha,deofcuyowhosenombrenamenonotquieroI wantacordarme.to remember.

Don Quijote — Miguel de Cervantes, 1605. “In a place in La Mancha, whose name I do not wish to remember.” Drag the slider: left glosses everything, right glosses nothing. In the Glossa reader this adapts automatically to your level and to the words you already know.

Limits, stated plainly: web app only (no native iOS/Android apps — it works in the browser, installable to the home screen), 18 languages, and books are the whole product — there’s no video or podcast mode. If you mostly learn from Netflix, Language Reactor below fits better.

2. LingQ — the all-media ecosystem

The veteran of the category. LingQ imports nearly anything — ebooks, web articles, YouTube videos, podcasts — and tracks every word’s status (new / learning / known) as you tap through. The ecosystem is unmatched in breadth, with audio, transcription, and spaced repetition built in. The trade-offs are equally well known: the interface is busy, the reading display is tap-to-translate (you leave the text to see a meaning), and the free tier caps at 20 saved words — a demo, in practice. Premium is $14.99/month ($119.99/year). If you want one subscription for all media types, this is the one; see our detailed Glossa vs LingQ comparison.

3. Readlang — the lean web reader

A long-standing favourite for good reason: upload an EPUB or TXT (or read any web page via the extension), tap words for instant translation, and get auto-generated flashcards from what you tapped. The free tier is genuinely usable — unlimited single-word translations, with phrase translations capped per day — and Premium is a modest $6/month. It’s web-only (no native mobile apps) and the polish is dated in places, but as a cheap, focused tap-to-translate reader it’s hard to argue with. Detailed comparison: Glossa vs Readlang.

4. Smart Book — the mobile power tool

A native iOS/Android reader with an enthusiast feature set: side-by-side parallel translation, a choice of translation engines (Google, DeepL, and LLM options), whole-chapter text-to-speech, and a personal dictionary that exports to Anki. Imports EPUB, FB2, and TXT, with a large free built-in library. Pricing is almost nominal — about $1.99/month or a one-time ~$25 unlock. The interface is dense and there’s no web version, but for reading offline on a phone with full control, it’s the strongest pick.

5. Linga — the tidy iOS-first reader

Similar shape to Smart Book with a cleaner, more Apple-native feel: import EPUB/PDF/MOBI/FB2/TXT, tap words or sentences for translation, offline text-to-speech, and built-in flashcard review. Around $5.49/month with a lifetime option. The significant catch: it supports learning only six languages (English, German, French, Spanish, Italian, Russian).

6. Beelinguapp — curated stories, not your books

Beelinguapp shows curated stories as side-by-side bilingual text with narrated audio highlighted karaoke-style — a pleasant, low-effort format for short daily reading. But you cannot import your own books, the catalog is stories and news rather than novels, and development has visibly slowed (the mobile app’s last update was mid-2024 as of this writing). Good as a gentle supplement; not a home for serious book reading.

7. Kindle — where the books are, with caveats

Kindle isn’t a learning app, but it’s where many people already buy foreign-language books, and Send-to-Kindle accepts your own EPUBs and PDFs. Tap a word for a dictionary entry or instant translation — serviceable for occasional lookups. Two things to know before committing: Word Wise, the feature everyone recommends, works only in English-language books — it helps learners of English, not English speakers learning something else — and there’s no interlinear or parallel display and no spaced repetition (Vocabulary Builder is a plain word list). Fine for strong readers; frustrating below B2.

8. Language Reactor — for video, with a text mode

Language Reactor is the standard tool for Netflix/YouTube learning (dual subtitles, popup dictionary), and it does have a lesser-known text mode that adds machine translation and TTS to pasted text and web pages — though there’s no native EPUB import, and it lives in a desktop Chrome extension with no mobile apps. Pro is around $6/month (the exact price sits behind a login). If books are your medium, the readers above fit better; if video is, this is the one to get.

9. LWT and LinguaCafe — free, if you host it yourself

Two open-source options for tinkerers. Learning With Texts is the ancient-but-working original: tap-to-translate with term tracking and Anki export, dated interface, runs on your own PHP server. LinguaCafe is the modern take — Docker-deployed, EPUB import, dictionary popups, built-in review — still pre-1.0, so expect rough edges. Cost: your time.

How to choose

Start from your medium and your books. If you learn from video, take Language Reactor. If you want one subscription across every media type and don’t mind a busy interface, take LingQ. If you read on your phone offline, Smart Book or Linga. If you want the cheapest capable web reader, Readlang. And if what you want is to open your own book and have exactly the hard words quietly explained under the line while you keep reading — that’s the case Glossa was built for, and the free tier is enough to test whether the approach fits you. Whichever you pick, the method matters more than the tool: how to learn a language by reading covers it.