Spaced repetition,
automated with FSRS
ClassFactor schedules every card with FSRS-6 — the modern successor to SM-2. It learns your personal forgetting curve for each card and brings it back right before you’d forget it. Maximum retention, minimum reviews, and nothing to configure.
- Powered by FSRS-6, not the old SM-2
- Predicts your forgetting curve per card
- Weakest recall surfaces first
- Included free on web, iOS, and Android
Free to start · no credit card required
Your review schedule
Cards resurface right before you’d forget them
How it works
You study. FSRS handles the timing.
There are no intervals to set and no schedule to build. Three things happen behind every review.
FSRS models each card
Every card gets its own memory model. FSRS-6 estimates how your memory of that specific card decays over time — its personal forgetting curve — from the way you grade it.
It schedules the perfect return
Instead of a fixed interval, each card is timed to resurface right before you would forget it. You never set an interval yourself — the algorithm does the math on every review.
You just study the daily queue
Open ClassFactor and work through the queue it hands you. Grade each card Again, Hard, Good, or Easy, and the next return date adjusts instantly.
What FSRS does for you
A scheduler that thinks about every card separately
Older apps apply one formula to everything. FSRS-6 gives each card its own memory model — and puts the right ones in front of you at the right time.
A forgetting curve per card
FSRS predicts memory decay for each card individually, not a one-size-fits-all interval — so an easy fact and a stubborn one are treated differently.
Grade, and the schedule reacts
Rate a card Again, Hard, Good, or Easy. A miss brings it back soon; an easy recall pushes it further out. The next interval recalculates on the spot.
Weakest recall comes first
The daily queue prioritizes the cards your memory is closest to losing, so the reviews that matter most happen before the ones that can wait.
Adapts to the time you have
Got ten minutes between classes or an hour before an exam? The queue adapts to the time you can give it and still surfaces what needs review first.
Every card type, one scheduler
Flashcards, multiple choice, cloze deletions, and image occlusion are all scheduled by the same FSRS engine — one queue for everything you study.
Nothing to configure
No intervals, ease factors, or graduating steps to tune. You bring the material and the grades; FSRS handles all the scheduling behind the scenes.
One grade, one tap
Every review teaches the scheduler
After you recall a card, you rate how it went. That single tap updates the card’s memory model and sets its next return — no math, no settings, no manual intervals.
The daily queue then reorders itself so your weakest recall is always first in line.
Your review schedule
Cards resurface right before you’d forget them
The science
Built on how memory actually works
FSRS isn’t a gimmick — it operationalizes decades of well-established learning science into a schedule tuned to you.
The forgetting curve
Memory fades predictably after you learn something. FSRS models that curve for each card so a review lands at the moment recall is about to slip — not too early, not too late.
The spacing effect
Reviews spread out over time build far more durable memory than the same effort crammed together. Spacing your recall is one of the most well-established findings in learning science.
Active recall
Retrieving an answer from memory strengthens it more than rereading ever could. Every card asks you to recall first, then grade — turning study time into the kind of practice that sticks.
Why it matters
Remember more, review less, plan nothing
Maximum retention
By timing each return to the edge of forgetting, FSRS keeps more of what you learn in memory for longer — without you tracking a thing.
Minimum reviews
No wasted reps on cards you already know cold, and no cramming cards you are about to lose. You do fewer reviews and remember more.
Zero planning overhead
You never decide what to study or when. Open the app, clear the queue, done. The hardest part of studying — being consistent — gets easier when the plan is made for you.
Your queue and schedule sync across web, iOS, and Android — generate on your laptop, review on your phone.
FAQ
Spaced repetition, answered
FSRS — the Free Spaced Repetition Scheduler — is the modern successor to the SM-2 algorithm that older flashcard apps use. ClassFactor uses FSRS-6, the latest version. Instead of applying a fixed formula to every card, FSRS builds a memory model for each individual card, predicting its personal forgetting curve so it can schedule the next review right before you would forget it.
No. You never set intervals manually. Just study the daily queue ClassFactor gives you and grade each card. FSRS calculates when every card should return, so there is nothing to configure — no ease factors, graduating steps, or interval settings to tune.
When you review a card you grade it — for example Again, Hard, Good, or Easy. That grade feeds the FSRS memory model: a card you miss comes back soon, while a card you recall easily is pushed further into the future. The next return date recalculates instantly with every review.
Yes. The same FSRS engine schedules every card and question type in ClassFactor — flashcards, multiple choice, cloze deletion, and image occlusion. They all flow into one daily queue that prioritizes your weakest recall first.
Yes. FSRS spaced repetition is included on every plan, the Free plan included. Your decks and their schedules sync across web, iOS, and Android, so you can review anywhere.
Spaced repetition is grounded in well-established cognitive science: the forgetting curve (memory fades predictably over time), the spacing effect (reviews spread out over time build more durable memory than cramming), and active recall (retrieving an answer strengthens it more than rereading). FSRS turns those principles into a schedule tuned to your own memory of each card.
Explore more
Works better with the rest of ClassFactor
Study once. Remember it for the exam.
Let FSRS schedule every card so it comes back right before you’d forget it. Free on every plan — no credit card.