FSRS Flashcards
The most advanced spaced repetition algorithm — schedules every card at the exact moment you need it.
What is FSRS?
FSRS (Free Spaced Repetition Scheduler) is an open-source, machine-learning-based spaced repetition algorithm. Unlike older algorithms like SM-2 (used by Anki), FSRS models your personal forgetting curve using 17 parameters — adapting to how *you* specifically remember and forget. Research shows FSRS achieves the same retention rate as SM-2 with 20–30% fewer reviews.
How FSRS Schedules Your Reviews
After reviewing a card, rate it: Again (forgot), Hard, Good, or Easy. FSRS uses these ratings to update its model of your memory.
FSRS calculates the exact probability that you'll remember a card on any given day. It shows the card just before the probability drops below your target retention (default: 90%).
Each rating shifts the next review interval. A card marked Easy gets a longer interval; one marked Again resets. FSRS continuously recalibrates based on your actual performance.
You can set a retention target (e.g., 80%, 90%, 95%). A higher target means more reviews; a lower target means fewer. MemoThings defaults to 90%.
FSRS vs SM-2 (Anki's Algorithm)
| Aspect | FSRS | SM-2 |
|---|---|---|
| Algorithm basis | Machine learning (DSR model) | Fixed formula (1987) |
| Personalisation | Adapts to your memory profile | Same intervals for everyone |
| Reviews needed | 20–30% fewer for same retention | Baseline |
| Retention target | User-configurable (e.g., 90%) | Fixed |
| Open source | Yes | Yes |
Study Modes That Work with FSRS
- Flashcard — classic front/back review with 4-level rating
- Quiz — multiple-choice; correct answers count toward FSRS rating
- Typing — type the answer; exact match required for Good/Easy rating
- Matching — pair cards; boosts recall through association
- Speed Round — timed review for high-confidence cards
- Listening — audio-first review for language learning
- True/False — fast binary judgement
- Fill in Blank — cloze deletion style
Frequently Asked Questions
- Is FSRS better than Anki's SM-2?
- Research consistently shows FSRS achieves the same retention rate with 20–30% fewer reviews than SM-2. This means less time studying for the same result. MemoThings implements FSRS natively with no plugins required.
- Can I import my Anki decks into MemoThings?
- MemoThings doesn't currently support direct Anki .apkg import. However, community decks covering the most popular Anki topics are available to import with one tap.
- What retention rate should I use?
- 90% is the standard recommendation — it balances review workload and retention well. If you're preparing for an exam, consider 93–95%. For casual vocabulary, 85% is often enough.
- Does FSRS work offline?
- Yes. The scheduling algorithm runs locally on your device. Card syncing requires an internet connection, but reviews can be completed offline and synced later.
Experience FSRS-powered flashcards
Download MemoThings free — FSRS scheduling is available on all plans.