Spaced Repetition: Study Less Often, Remember Way More
Most of what you learn in lecture fades within days unless you come back to it. Spaced repetition brings each fact back right before you'd forget it, so it sticks until finals and beyond. Here's how it works and how to set it up in a few minutes.
The Forgetting Curve: Why Last Week's Lecture Is Already Fuzzy
In 1885, German psychologist Hermann Ebbinghaus memorized lists of nonsense syllables and tested himself at different delays. He found that memory drops fast at first, then levels off: a big chunk is gone within a day, and what's left keeps slipping over the following week. You've felt this. You understood it in class, and three days later it's a blur.
Without review
Most of it slips away within a few days
Illustration based on Ebbinghaus's forgetting curve (1885). Real numbers vary a lot with the material and how well you learned it the first time.
With spaced repetition
Every review makes the next gap longer
Day 1
First review
90% recall
Day 3
Second pass
85% recall
Day 7
Getting solid
88% recall
Day 14
Longer gaps
92% recall
Day 30
Long-term
95% recall
Example schedule. With FSRS, each card gets its own intervals based on your answers, and Revizly aims to show it to you when you're still about 90% likely to remember it.
How to Use Spaced Repetition with Revizly
The method is simple. Doing it by hand is not: you'd have to write every card and track every due date yourself. Revizly handles both.
Add your class material
Upload a PDF or your lecture slides, snap photos of your handwritten notes, paste a YouTube lecture link, or paste text.
Get flashcards in a minute or two
Revizly's AI pulls out the definitions, key concepts, formulas and dates worth memorizing and turns them into flashcards, along with a study guide and a practice quiz.
Review what's due, nothing more
Mark each card as known or not. FSRS uses your answers to pick when each card comes back: soon if you missed it, later and later as it sticks.
Why Spaced Repetition Works So Well
The spacing effect is one of the most replicated findings in learning research. Here's what that means for you.
Backed by real research
Psychologists have studied the spacing effect since Ebbinghaus. A 2006 review by Cepeda and colleagues pooled hundreds of experiments and found spaced practice beat massed practice again and again.
Better than rereading
Rereading feels productive because the material looks familiar. Flashcards make you actually pull the answer from memory, and that effort is what makes it stick.
Adapts to you
FSRS tracks how each card is going for you. Cards you keep missing come back often, and cards you know cold get pushed out so you stop wasting time on them.
Lasts past the exam
Cramming can get you through tomorrow's quiz, but it fades fast. Spaced reviews build memory you still have at finals, and in the next class that builds on this one.
FSRS vs. Other Ways to Study
A rough comparison of common study methods, based on what learning research says about spacing and active recall.
| Method | How much sticks | Time well spent | Adapts to you | Long-term |
|---|---|---|---|---|
Spaced repetition (FSRS) | Very high | Excellent | Automatic | |
Leitner box system | High | Good | Manual | |
Reviewing when you remember to | Medium | Fair | None | |
Rereading your notes | Low | Poor | None |
Fixed intervals (1-3-7-14-30)
Reviewing on day 1, 3, 7, 14 and 30 is spaced repetition done by hand. It works, but every card gets the same schedule. FSRS sets the gaps card by card based on how you actually answer.
Leitner system
Cards move between boxes as you get them right or wrong, and each box is reviewed less often. Solid low-tech method, but you manage the boxes yourself and the schedule is coarse.
Cramming
An all-nighter before the exam can get you a passing grade, but most of it is gone a week later. Then you relearn it all for the final. Same effort, spread out, gets you much further.
Spaced Repetition, Explained
The research behind it
Two ideas do most of the work. The first is the spacing effect: the same amount of study time leads to better memory when it's spread over days instead of packed into one session. The second is retrieval practice: trying to recall an answer strengthens memory more than reading it again. Flashcards on a spaced schedule combine both.
This isn't a new or fringe idea. In 2006, Cepeda and colleagues published a meta-analysis covering more than 250 studies of distributed practice and found a consistent advantage for spacing. In 2013, a widely cited review by Dunlosky and colleagues rated distributed practice and practice testing as the two most useful study techniques out of the ten they examined.
Using it for midterms, finals and big exams
Med students are famous for it. Prepping for the USMLE means memorizing a huge volume of facts, and many students rely on daily spaced repetition flashcards to keep up, because cramming that much simply doesn't work.
It works just as well outside of med school: biology and chemistry terms, history dates, legal rules, vocab for a language class, formulas for stats. The trick is to start early. Make cards right after each lecture and do a short review every day, so finals week is a refresher instead of a rescue mission.
Why FSRS beats older algorithms
For decades, most flashcard apps used some version of SM-2, an algorithm from 1987 that grows intervals with fixed multipliers. FSRS (Free Spaced Repetition Scheduler) is a newer, open-source algorithm that models how memory actually decays, using your full review history to estimate how likely you are to remember each card at any moment.
In the project's public benchmarks, built on millions of real Anki reviews, FSRS predicts forgetting more accurately than SM-2, and its developers estimate it needs about 20 to 30% fewer reviews for the same retention. That's the scheduler behind every Revizly flashcard, on the web and in the app.
Try Spaced Repetition Free
Upload notes from one of your classes and get a flashcard deck scheduled with FSRS. Free to start, no credit card.
Get started freeSpaced Repetition FAQ
What is spaced repetition?
Spaced repetition is a study method where you review material at gradually longer intervals instead of all at once. You might see a flashcard again after a day, then a few days, then a week or more, and each successful review pushes the next one further out. It works with how memory naturally fades, so you put in less total time and remember more. The idea goes back to Hermann Ebbinghaus's forgetting curve experiments in 1885.
How does the FSRS algorithm work?
FSRS (Free Spaced Repetition Scheduler) is an open-source algorithm that estimates how likely you are to remember each card based on your review history. When you get a card right, its next review moves further out. When you miss it, it comes back soon. In Revizly, it schedules each card for when you're still about 90% likely to remember it, so you review just before you'd forget. Its developers' benchmarks show it predicts forgetting more accurately than SM-2, the older algorithm many flashcard apps still use.
Does spaced repetition actually work?
Yes. It's one of the best-supported findings in learning research. A 2006 meta-analysis by Cepeda and colleagues, covering more than 250 studies, found that spreading practice out consistently beats massing it together. A 2013 review by Dunlosky and colleagues rated spaced practice and self-testing as the most useful study techniques they looked at, well ahead of rereading and highlighting. Results depend on the material and how consistent you are, but the direction is clear.
What's the difference between Revizly and Anki?
Anki is a great spaced repetition app, and recent versions can use FSRS too. The catch is that you write every card yourself, which can eat hours. Revizly builds the cards for you: upload a PDF, lecture slides, photos of your notes or a YouTube lecture, and you get flashcards scheduled with FSRS, plus a study guide and a practice quiz. If you love Anki, Premium lets you export your decks to it.
How do I start using spaced repetition with Revizly?
Create a free account, add material from one of your classes (PDF, lecture slides, photos of your notes, a YouTube link or pasted text), and Revizly generates your flashcards. Then just review the cards that are due each day. FSRS takes care of the schedule, so there's nothing to set up. The free plan lets you try it on two classes a month, no credit card needed.