How Spaced Repetition Works
The science-backed method that helps you remember anything — permanently.
The Forgetting Curve
Each card has its own forgetting curve. Rate how well you remember, and watch how the algorithm schedules your next review. Try it — click a rating to begin.
Review Session 1
This card is new. Rate how well you know it to begin.
Self Rating
This tells the algorithm when this card should come up again.
How BrainLS Works
Create Cards
Add flashcards with rich markdown, images, cloze deletions, or multiple choice. Organize them into decks and folders.
Study & Rate
When you study a card, rate how well you knew the answer. The algorithm adjusts the next review time based on your response.
Review on Schedule
Cards reappear at optimal intervals. Easy cards come back less often. Difficult cards come back sooner until you master them.
The FSRS Algorithm
BrainLS uses FSRS (Free Spaced Repetition Scheduler), a modern algorithm that outperforms older systems like SM-2 used in traditional flashcard apps.
FSRS tracks two key properties for each card: stability (how well the memory is consolidated) and difficulty (how inherently hard the card is for you). Together, these determine the optimal review time to maintain your desired retention rate.
Default target — you'll remember 95 out of 100 cards at review time.
New cards go through short learning intervals (1min, 10min) before entering the long-term review schedule.
Common Questions
Can I review a card before it's due?
Yes, but it's less efficient. The algorithm works best when you review right around the scheduled time. Reviewing too early means the memory hasn't had time to weaken, so the strengthening effect is smaller.
What happens if I miss a review day?
Nothing catastrophic. When you eventually review the card, the algorithm sees how long it's been and adjusts accordingly. Your retention will have dropped, but a single successful review gets you back on track — the next interval will just be shorter than if you'd reviewed on time.
What do the rating buttons mean?
Again/Don't Know: you didn't remember at all. Hard: you recalled it but with significant effort. Good: you recalled it with moderate effort. Easy: it was effortless. The algorithm uses your rating to decide how soon you'll see the card again.
How many new cards should I learn per day?
Start with 10–20 new cards per day. Adding too many at once creates a review backlog that snowballs. It's better to be consistent with a smaller number than to binge and burn out.
What's the difference between Learning and Review?
New cards go through short learning steps (1 minute, then 10 minutes) before entering the long-term review schedule. This initial repetition helps form the memory before the algorithm starts spacing reviews over days and weeks.