Leitner

The Leitner system, also known as the Leitner method, is a technique for spaced repetition using flashcards. It was developed by German educator Sebastian Leitner in the 1970s and has since become a widely cited approach for organizing study reviews based on recall performance.

The method uses a set of five boxes. Each flashcard starts in Box 1. When a card is reviewed, the learner attempts to recall the answer. If the recall is correct, the card moves to the next box; if it is incorrect, the card returns to Box 1. Each box has a different review frequency, with Box 1 reviewed daily and successive boxes reviewed at increasing intervals (commonly Box 2 every two days, Box 3 every four days, Box 4 every eight days, and Box 5 every sixteen days). Cards in higher boxes are revisited less often, under the assumption that remembered material requires fewer reviews over time.

The Leitner system emphasizes retrieval practice and spaced repetition, offering a simple, low-tech framework that can be implemented with physical index cards or digital flashcard software. It provides a visually intuitive way to prioritize weaker material while maintaining regular exposure to stronger knowledge.

Impact and variations: The Leitner method remains influential in education and self-study. Many modern flashcard applications incorporate Leitner-like elements or hybrid scheduling that blends box-based review with adaptive intervals. While praised for its simplicity, critics note that fixed box schedules may not fit all content or forgetting patterns, and some learners benefit from more flexible, data-driven spacing algorithms.