What is FSRS spaced repetition?

FSRS (Free Spaced Repetition Scheduler) is a state-of-the-art algorithm backed by peer-reviewed research. It calculates the optimal review time for each word based on your performance, scheduling difficult words more frequently and easy ones less often to maximize long-term retention.

Why are words ordered by frequency?

Courses contain up to 10,000 words sorted by how often they appear in real usage. Learning the most common words first means you can start having real conversations faster and understand more of what you read and hear.

What happens without spaced repetition?

Research by Hermann Ebbinghaus showed that without review, you forget 56% after 1 hour, 66% after 1 day, and 75% after 6 days. MassVocabulary schedules reviews at the exact moment before you forget, turning short-term memorization into lasting knowledge.

Closed Beta

Master Vocabulary with Science-Backed Spaced Repetition

Q: How does MassVocabulary teach vocabulary?

Each word is presented within a real example sentence. During review, the target word is hidden and you recall it from context, training your brain to use words naturally. This contextual approach combined with FSRS spaced repetition ensures lasting retention.

Q: Does MassVocabulary work offline?

Yes. Your vocabulary database lives on your device so you can study anywhere without internet. When you're back online, cloud sync keeps your progress updated across all devices.

Join a growing community of learners. MassVocabulary uses the FSRS algorithm to help you memorize words efficiently and retain them long-term.

📚10,000 Words

🧠FSRS Algorithm

💬Learn in Context

📱Offline Ready

Supported Languages

🇳🇴Norwegian

🇻🇳Vietnamese

🌍More coming soon

Try It Yourself

Experience how MassVocabulary teaches — learn new words first, then review them from context.

LearningLearning 1 of 5

hei

/hɛi/

hello, hi

interjection

A common informal greeting used when meeting someone.

Hei, hvordan har du det?

Hello, how are you?

This is a simplified preview. The full app includes native speaker audio, spaced repetition scheduling, and thousands of words.

How It Works

MassVocabulary combines frequency-ordered vocabulary with contextual learning and spaced repetition for maximum retention.

Learn Words in Context

Each word is presented within a real example sentence, showing you how it's actually used in natural speech.

Learning screen displaying a Vietnamese word with its translation, example sentence, and audio playback controls

Recall from Context

During review, the target word is hidden. You recall it from the sentence context, training natural usage.

Review screen showing an example sentence with the target word hidden, prompting the user to recall the vocabulary from context

Smart Scheduling

FSRS calculates the optimal review time for each word. Difficult words appear more often, easy ones less frequently.

Statistics screen with retention rate charts, 30-day review forecast, and learning progress metrics per course

The Forgetting Curve

Without Spaced Repetition, You Lose What You Learn

Research by Hermann Ebbinghaus showed that memory decays exponentially. Every word you study without a review schedule is a word you'll forget.

56%

After 1 hour

forgotten without review

66%

After 1 day

forgotten without review

75%

After 6 days

forgotten without review

With FSRS spaced repetition, our community retains vocabulary long-term — MassVocabulary schedules reviews at the exact moment before you forget, turning short-term memorization into lasting knowledge.

Research & Citations

How We Compare

MassVocabulary combines the best spaced repetition science with curated content and a polished experience — so you can focus on learning, not configuring.

Spaced Repetition

MassVocabulary

FSRS — state-of-the-art algorithm

Anki

SM-2 (1987) / FSRS opt-in

Duolingo

Proprietary, lesson-based

Memrise

Basic interval system

Babbel

Simple review, no SRS

Vocabulary Depth

MassVocabulary

10,000 frequency-ordered words per language

Anki

Varies by community deck

Duolingo

~2,000-4,000 words per course

Memrise

Community-created, inconsistent

Babbel

~3,000 words per course

Contextual Sentences

MassVocabulary

Every word with example sentence

Anki

Depends on deck creator

Duolingo

Translation exercises only

Memrise

Video clips for some words

Babbel

Dialogue-based context

Native Audio

MassVocabulary

Included for all words

Anki

Rarely included

Duolingo

TTS for most content

Memrise

Native speaker video clips

Babbel

Professional recordings

Offline Support

MassVocabulary

Full offline-first, study anywhere

Anki

Full offline support

Duolingo

Premium only, limited

Memrise

Premium only

Babbel

Download lessons for offline

Pricing

MassVocabulary

Free during beta

Anki

$25 on iOS / free elsewhere

Duolingo

Free with ads / $84/yr premium

Memrise

$60-120/yr for full access

Babbel

$84-168/yr

Setup Required

MassVocabulary

None — pick a course, start learning

Anki

Find decks, install add-ons, configure

Duolingo

Minimal — choose a language

Memrise

Minimal — choose a course

Babbel

Minimal — choose a language

Focus on Vocabulary

MassVocabulary

100% vocabulary-focused mastery

Anki

Flashcard tool, not language-specific

Duolingo

Grammar, stories, games mixed in

Memrise

Mixed vocabulary and phrases

Babbel

Conversation and grammar focus

	MassVocabulary	Anki	Duolingo	Memrise	Babbel
Spaced Repetition	FSRS — state-of-the-art algorithm	SM-2 (1987) / FSRS opt-in	Proprietary, lesson-based	Basic interval system	Simple review, no SRS
Vocabulary Depth	10,000 frequency-ordered words per language	Varies by community deck	~2,000-4,000 words per course	Community-created, inconsistent	~3,000 words per course
Contextual Sentences	Every word with example sentence	Depends on deck creator	Translation exercises only	Video clips for some words	Dialogue-based context
Native Audio	Included for all words	Rarely included	TTS for most content	Native speaker video clips	Professional recordings
Offline Support	Full offline-first, study anywhere	Full offline support	Premium only, limited	Premium only	Download lessons for offline
Pricing	Free during beta	$25 on iOS / free elsewhere	Free with ads / $84/yr premium	$60-120/yr for full access	$84-168/yr
Setup Required	None — pick a course, start learning	Find decks, install add-ons, configure	Minimal — choose a language	Minimal — choose a course	Minimal — choose a language
Focus on Vocabulary	100% vocabulary-focused mastery	Flashcard tool, not language-specific	Grammar, stories, games mixed in	Mixed vocabulary and phrases	Conversation and grammar focus

Each app has its strengths. MassVocabulary is purpose-built for vocabulary mastery with the latest spaced repetition research.

Everything You Need to Master Vocabulary

Built with proven learning science and designed together with our community of serious language learners.

10,000 Frequency-Ordered Words

Learn the most important words first. Courses contain up to 10,000 words sorted by how often they appear in real usage, so you can start having real conversations faster.

Contextual Learning with Word Hiding

Every word comes with an example sentence. During review, the target word is hidden and you recall it from context—training your brain to use words naturally.

FSRS Spaced Repetition

Built on the state-of-the-art FSRS algorithm, backed by peer-reviewed research and used by millions of learners worldwide. MassVocabulary calculates the perfect time to review each word based on your performance, ensuring long-term retention.

Based on the Free Spaced Repetition Scheduler by Jarrett Ye et al.

Audio Learning

Every word comes with native pronunciation. Hear the word, hear it used in context. Audio playback helps cement pronunciation and improves listening comprehension.

Detailed Analytics

See exactly how you're progressing. Track retention rates, learning stability, and more. The 30-day forecast shows what's coming up so you can plan your study sessions.

Cloud Sync & Offline

Your vocabulary database lives on your device. Study anywhere without internet. When you're back online, cloud sync keeps your progress updated across all devices.