What is spaced repetition? A practical guide to SRS

What SRS actually means

Imagine learning a new Spanish phrase on Monday. You try to recall it later, check the answer, and return to it in another session. If it comes easily, you can leave a longer gap. If you draw a blank, it needs more attention.

That’s the basic routine. A flashcard system stores the question, the answer, and your review history. A scheduler decides which cards are due. Spaced repetition is the study method; an SRS is a tool for organizing it.

The schedule is only one part of the job. You still have to choose useful material, understand it, and make an honest attempt to answer. Moving through a queue while immediately revealing every answer misses the recall step.

Spacing and recall do different jobs

Spacing separates learning sessions over time. In their 2006 review of verbal recall experiments, Nicholas Cepeda and colleagues found that effective spacing depended partly on how long learners needed to retain the material. There isn’t one ideal interval for every goal. Read the distributed practice review.

Active recall means trying to produce an answer before looking at it. Jeffrey Karpicke and Henry Roediger’s vocabulary study found that continued retrieval after an item was first learned improved later recall. Read the retrieval study.

In a flashcard review, these ideas meet: the system brings back a question after a gap, and you try to answer it. Their findings concern spacing and retrieval practice. Retri brings those methods into a flashcard workflow.

Try a review with one real question

Suppose you’ve just used ChatGPT to understand the difference between an HTTP 401 response and a 403 response. After checking the explanation against the relevant documentation, write a question you might need to answer at work:

The example follows the status definitions in HTTP Semantics (RFC 9110).

Before revealing the back, say or type your answer. If you only remembered “some kind of access error,” the distinction still needs practice. If you answered clearly, rate that recall honestly and let the system plan another review.

You can also write a separate scenario card about what you would check next. Keeping a definition and a debugging decision separate makes each question easier to judge.

What a scheduler can and can’t know

Retri uses FSRS-6, an open-source spaced repetition scheduler. It updates a card’s memory state from reviews and uses that state to plan intervals. The project’s FSRS introduction explains the model.

A scheduler estimates. It doesn’t measure your memory directly or know the exact moment you’ll forget. Your rating is useful input, so avoid marking a card easy because its answer looks obvious after you reveal it.

In Retri, you can rate a review Again, Hard, Good, or Easy. Use Again when you couldn’t recall the answer. Save a positive rating for an answer you actually produced, with the other ratings reflecting how difficult that successful recall felt.

Start with a deck you can keep reviewing

For a first experiment, choose one subject you expect to use again and make a small set of questions. Start with a handful of cards from a useful conversation so you can learn how the routine fits your day.

Review the due cards before creating another large batch. Rewrite questions that confuse you, and suspend cards you no longer need. If the queue becomes a chore, reduce what you add.

Flashcards work best as part of a broader practice. Use vocabulary in conversation, write code, explain ideas in your own words, and solve problems with unfamiliar examples. Remembering a definition is a useful foothold, but you also need to use it.

Ready to try it in chat? Follow our ChatGPT spaced repetition workflow or read the Retri setup guide.