Spaced repetition · FSRS

Study once. Remember for months.

GoodOff uses the FSRS algorithm to calculate the optimal moment to review every card. Each review strengthens the memory and pushes the next one further out. You stop forgetting.

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How it works

How spaced repetition works.

The forgetting curve shows memory decaying over time. Spaced repetition intercepts the decay — each review resets the curve higher and flatter.

Without review With spaced repetition
100%50%0%Day 1TimeMonthsIntervals grow
01

Learn

See a card for the first time. Rate your recall: Again, Hard, Good, or Easy.

02

Forget (a little)

FSRS calculates when you'll start to forget based on your rating and history.

03

Review at the right moment

The card reappears right before the memory fades. Each recall strengthens the trace.

04

Intervals grow

As memory strengthens, intervals stretch from minutes to days to weeks to months.

Why FSRS

Why FSRS beats older algorithms.

FSRS is an open-source algorithm that models memory mathematically. It replaced SM-2 as the recommended algorithm in Anki and is built into GoodOff natively.

FeatureFSRS (GoodOff)SM-2 (Anki)LeitnerFixed
Adapts to each cardYesPartiallyNoNo
Models the forgetting curveYesNoNoNo
Recall gradesAgain / Hard / Good / Easy0–5 scalePass / FailN/A
Interval calculationMachine-learned parametersFixed multiplier formulaBox promotionManual
Differentiates easy vs hardYesLimitedNoNo

FSRS was developed as an open-source project and benchmarked against SM-2 by the Anki community. GoodOff implements FSRS natively — no add-ons or manual configuration required.

What you get

Built for real studying.

Every feature serves the same goal: reviewing each card at exactly the right moment, in the format that works for you.

FSRS algorithm

The Free Spaced Repetition Scheduler predicts when you'll forget each card and schedules the review right before that happens.

Memory strengthening

Each successful recall strengthens the memory trace. Cards move through states — New, Learning, Review — as they solidify.

Optimal timing

Intervals grow automatically: minutes after your first review, then days, then weeks, then months. You focus on what needs work.

Adaptive difficulty

Rate each card Again, Hard, Good, or Easy. FSRS adjusts the next interval based on your specific response — not a one-size-fits-all formula.

Multiple study modes

Classic flip, multiple choice with a 30-second timer, vertical swipe, or full-screen focus. Same FSRS scheduling, different formats.

Retention targets

Set your desired retention rate and let the algorithm adjust intervals to hit it. Power users can tweak multipliers to match their goals.

The research

Why spaced repetition works.

Over a century of cognitive science supports it. These are the core principles.

The forgetting curve

Hermann Ebbinghaus (1885) demonstrated that memory decays exponentially without reinforcement. Each well-timed review resets the curve at a higher baseline, making the next decay slower.

Retrieval practice

Actively recalling information strengthens memory far more than passive re-reading. This is the testing effect, confirmed across hundreds of studies (Roediger & Karpicke, 2006).

Distributed practice

Spacing study sessions apart produces stronger long-term retention than massing them together — one of the most replicated findings in cognitive psychology (Cepeda et al., 2006).

Desirable difficulty

Retrieving a memory when it's slightly difficult — not impossible, but not effortless — produces the strongest encoding. FSRS targets this sweet spot (Bjork, 1994).

Built for how you study

Works for every subject.

For medical students

MCAT, USMLE, board prep. High-volume memorization across anatomy, pharmacology, and pathology. Import your existing Anki decks or generate new ones from lecture notes.

For law students

Case law, statutes, legal principles. Spaced repetition turns rote memorization of case holdings and statutory elements into durable recall for the bar exam.

For language learners

Vocabulary acquisition, grammar patterns, conjugation tables. FSRS adapts interval length to each word's difficulty for you specifically.

Deeper look

What is spaced repetition?

Spaced repetition is a learning technique rooted in over a century of cognitive science. In 1885, Hermann Ebbinghaus published his research on the forgetting curve — the observation that newly learned information decays exponentially unless reinforced. The core principle is straightforward: instead of cramming, space out your reviews at increasing intervals. Each successful recall at the right moment strengthens the memory trace and slows the rate of forgetting.

Modern implementations use algorithms to automate the scheduling. GoodOff uses FSRS (Free Spaced Repetition Scheduler), which models two properties of each card: stability (how resistant the memory is to forgetting) and difficulty (how inherently hard the card is for you). When you rate a card Again, Hard, Good, or Easy, FSRS updates both values and calculates the next optimal review time. Cards you struggle with appear more frequently; cards you know well fade into longer intervals.

How GoodOff uses it

Upload lecture notes, PDFs, or textbook chapters, and the AI generates flashcards optimized for spaced repetition. The FSRS algorithm schedules your daily reviews. Combined with gamification — XP, streaks, and leaderboards — GoodOff turns a well-researched study method into a daily habit. You can also import existing Anki decks (.apkg format) and pick up where you left off with your existing scheduling data.

Common questions

Spaced repetition FAQ

What is spaced repetition?+
Spaced repetition is a study method that schedules review sessions at increasing intervals. Instead of cramming everything at once, you review each piece of information right before you're likely to forget it. Each successful recall strengthens the memory, and the interval until the next review grows longer. The technique is grounded in over a century of cognitive science, starting with Ebbinghaus's 1885 research on the forgetting curve.
How does FSRS compare to Anki's SM-2 algorithm?+
FSRS (Free Spaced Repetition Scheduler) is a newer, open-source algorithm that uses a mathematical model of memory to predict when you'll forget each card. SM-2, Anki's default, uses a simpler fixed-multiplier formula that doesn't model forgetting directly. In community benchmarks, FSRS produces more accurate predictions of recall probability. GoodOff uses FSRS natively — no add-ons needed.
How often should I review flashcards?+
There's no single answer — that's the whole point of spaced repetition. FSRS calculates the optimal review time for each card individually based on your past responses. New or difficult cards might come back in minutes or hours. Well-known cards might not appear for weeks or months. You don't set the schedule; the algorithm does.
Is spaced repetition better than cramming?+
For long-term retention, yes. Cramming can work for a test tomorrow, but the information fades rapidly afterward. Spaced repetition distributes practice across time, which produces significantly stronger long-term memory. This is the distributed practice effect, one of the most replicated findings in cognitive psychology (Cepeda et al., 2006).
Do I need Anki to use spaced repetition?+
No. GoodOff implements the FSRS algorithm natively with a modern interface, AI-powered card generation from your PDFs and notes, gamification (XP, streaks, leaderboards), and multiple study modes. You can also import existing Anki .apkg decks if you want to bring your cards over.
Does spaced repetition work for medical school?+
Spaced repetition is widely used by medical students preparing for USMLE, MCAT, and board exams. The technique is well-suited for high-volume memorization — anatomy terms, drug mechanisms, pathology classifications. Many med students combine spaced repetition with active recall to retain large volumes of material across semesters.
What's the difference between spaced repetition and re-reading?+
Re-reading is passive — you see the material and feel familiar with it, but that familiarity doesn't mean you can recall it on a test. Spaced repetition forces active recall: you see a question, try to retrieve the answer, then check. The retrieval effort is what strengthens the memory, not the exposure.
Is there an optimal spaced repetition interval?+
There's no single optimal interval — it depends on the card, the learner, and how many times you've successfully recalled it. FSRS calculates the interval per card based on your history of responses. A card you rated "Easy" three times in a row gets a much longer interval than one you just rated "Again." The algorithm handles this automatically.
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Spaced Repetition — FSRS Flashcards That Actually Stick | GoodOff