Spaced Repetition

Spaced repetition is a study method based on the spacing effect — the well-established finding that distributing practice over time produces dramatically better long-term retention than massing practice into a single session (cramming). The concept dates back to Ebbinghaus's memory experiments in the 1880s, but the first practical spaced repetition systems emerged in the 1970s with Sebastian Leitner's cardboard box system. The field was transformed by Piotr Wozniak's SuperMemo algorithm (SM-2) in 1987, which introduced computer-scheduled intervals based on self-reported recall quality.

Modern spaced repetition systems have evolved far beyond SM-2's simple heuristics. The latest generation, exemplified by FSRS (Free Spaced Repetition Scheduler), uses mathematical models of memory decay to predict exactly when you will forget each individual item and schedules the review just before that moment. This approach is grounded in the forgetting curve research: each successful retrieval strengthens and stabilises the memory, pushing the optimal review point further into the future. The result is a system that automatically concentrates your study time on the material you are most likely to forget.

Revu is built entirely around spaced repetition powered by FSRS. Every card you study is tracked individually with its own memory parameters — stability, difficulty, and predicted retrievability. The algorithm considers your personal learning patterns, the inherent difficulty of each card, and your target retention rate to compute the optimal moment for each review. This means you spend your study time where it matters most, achieving high retention rates across large volumes of material with a fraction of the time that traditional study methods require.