In short
Spaced repetition means testing yourself instead of re-reading, and spacing the reminders at the right moment. Two simple ideas that together make you remember far longer for far less effort. An algorithm such as FSRS works out those intervals for you.
What is spaced repetition?
Spaced repetition is a learning technique built on reviewing information at growing intervals: first after a day, then after a few days, then a week, a month, and so on. Every successful review pushes the next one a little further out. So you review less often, but at the right moment.
The starting point: the forgetting curve
In the late 19th century, psychologist Hermann Ebbinghaus showed that we forget what we have just learned very quickly: much of it disappears within days if nothing refreshes the memory. That is the forgetting curve.
Every successful recall flattens that curve: the information then fades more slowly. Spaced repetition exploits exactly this mechanism — it places a reminder just before the curve drops.
The real engine: testing yourself (active recall)
Re-reading, highlighting, copying out: these feel reassuring but stick poorly. The most powerful lever is active recall: forcing your brain to retrieve the answer before seeing it. It is the retrieval effort that carves the memory in.
That is why spaced repetition relies on question/answer cards: you answer first, you check afterwards. Question first, never the solution.
Spacing at the right moment
Reviewing too early wastes time on what you already know. Review too late and you have forgotten everything: you relearn from scratch. The right interval sits exactly between the two — late enough for the recall effort to be real, early enough for the memory to still be there.
Working that moment out card by card, by hand, is impossible. That is the job of an algorithm such as FSRS, which adapts to your memory from your answers.
How to get started in practice
- Write short cards: one idea per card, a clear question, a precise answer. Three good cards beat thirty vague ones.
- Answer before flipping the card, even in your head. No recall effort, no memorisation.
- Be honest about what you actually knew: that is what lets the algorithm plan the next step properly.
- Come back regularly, a little every day, rather than everything the night before. Consistency beats intensity.
Frequently asked questions
What is spaced repetition?
Spaced repetition means testing yourself instead of re-reading, and spacing the reminders at the right moment. Two simple ideas that together make you remember far longer for far less effort. An algorithm such as FSRS works out those intervals for you.
Which app should you use for spaced repetition?
Memnos is a web flashcard app built on spaced repetition: you paste your notes, it turns them into question/answer cards and the FSRS algorithm schedules every reminder. Free, with a no-account trial. Anki is the other reference, more powerful but longer to set up.
How much time a day does it take?
A few regular minutes are often enough: the whole point of the method is to cut the volume of reviews. Ten minutes a day beats one long weekly session.
Does spaced repetition work for everything?
It shines for anything memorised as facts, definitions, vocabulary or formulas. For practical skills it complements training rather than replacing it.
Go from theory to practice
Paste your notes, Memnos turns them into cards and schedules the reminders at the right moment. No account needed.
Try without an account