Spaced repetition tries to show a card near the point where recalling it becomes difficult. Review too soon and the answer is still obvious. Wait too long and you have to learn it again. FSRS—the Free Spaced Repetition Scheduler—uses a card's review history to estimate a useful next interval.

Audio Flashcards uses FSRS for graded reviews. The fact that a card is spoken rather than displayed does not change the scheduling problem: the app still needs to know whether you remembered it and how much effort it took.

One history for each card

Every card develops its own schedule. A fact you know well may move from days to weeks or months. A similar-looking card that you repeatedly miss can continue returning much sooner.

The scheduler learns from the sequence of grades, not simply from the number of times the card has been played. Hearing a card while distracted is different from successfully recalling its answer.

What the four grades mean

After the answer, choose the grade that best describes the recall:

How Again, Hard, Good, and Easy lead to progressively longer next intervals

  • Again: you did not remember the answer, or your answer was substantially wrong.
  • Hard: you reached the answer, but only slowly or with considerable uncertainty.
  • Good: you recalled the answer with the normal amount of effort.
  • Easy: the answer was immediate and felt much easier than expected.

The labels are deliberately about the experience of recall. They are not percentages and do not need to be distributed evenly.

Audio Flashcards shows a proposed interval beside every grade. That lets you see the consequence before choosing: Again might return in minutes, while Easy might wait for weeks. The real numbers depend on the card's history and your settings.

Desired retention

Desired retention describes how likely you want to be to remember a card when it next appears. A higher target generally produces shorter intervals and more reviews. A lower target allows longer intervals and accepts that more cards will be forgotten.

There is no single perfect value for every library. Material for an imminent exam may justify more frequent review than a large background-knowledge collection. The important thing is to avoid changing the target constantly: the schedule becomes more useful when it can respond to a stable goal.

The exact controls, recalculation behaviour, and maximum interval are documented in FSRS Scheduling and Retention Settings.

Practice without changing the schedule

Sometimes you want extra exposure without telling the scheduler that the card was due. A practice session can study ahead without changing review progress. This is useful before a test, presentation, or journey where you want a particular set available.

Saved Review Sessions remember whether they record progress, which cards they include, and whether they focus on due cards.

What about cards you only hear?

A hands-free session may play a card all the way through without receiving a grade. By default, simply hearing it does not move its FSRS due date: the app has no evidence that you recalled the answer.

Audio Flashcards also offers a separate passive scheduler. When enabled for a session, it spaces out cards that were played but not graded, preventing a listening session from repeating the same small set forever. Passive scheduling is intentionally separate from FSRS because listening and active recall are not the same signal.

See Active recall vs passive listening for how to use both kinds of session without confusing their purpose.

A sustainable review habit

The schedule works best when the cards are short, the grades are honest, and reviews happen often enough that the queue remains manageable. If one card keeps returning, inspect the card before blaming the algorithm. It may contain several facts, use ambiguous wording, or need context.

The Statistics tab shows grade mix, future workload, and the history of individual cards. Statistics explains how to read those views and find cards that need attention.