Guide · Study science
The Leitner system is the classic paper-and-box version of spaced repetition. It is a clever, low-tech way to space your reviews — and understanding it makes it obvious why most people now let software run the boxes for them.
Invented by Sebastian Leitner in the 1970s, the system uses a row of boxes — commonly five. Every flashcard lives in one box, and the box decides how often you review that card. Box 1 holds the cards you see most often; each higher box is reviewed less frequently. A card climbs or falls based on whether you get it right.
Label five containers Box 1 to Box 5 and start every new card in Box 1.
Each day review Box 1; on the right days review the slower boxes per your schedule.
Correct cards move up a box; missed cards go back to Box 1. Repeat daily.
The Leitner system is really a coarse approximation of spaced repetition: fixed boxes, fixed intervals. Modern algorithms like SM-2 do the same thing more precisely — they set a custom interval for every card based on how hard you found it, instead of lumping cards into five buckets. Brainfy runs an SM-2-style scheduler so you get Leitner's logic without sorting physical cards. If you want the full picture, read our spaced repetition guide.
Classically five, though you can use three or seven. More boxes mean more gradations of review frequency.
It drops back to Box 1 and returns to frequent review until you get it right again, then it starts climbing once more.
It is an early, manual form of it. Algorithms like SM-2 do the same job with smoother, per-card intervals instead of fixed boxes.
Boxes work but are fiddly to maintain and easy to forget. An app schedules each card automatically and shows you only what is due.
Absolutely — the Leitner method is a fine low-tech option. Many learners start on paper and move to an app once the deck grows.
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