What to look for in a spaced-repetition app

A spaced-repetition app is a flashcard app that decides when you review each card — spacing reviews out so you see a card right before you would forget it. That core idea is backed by decades of research on the spacing effect, and most modern apps implement it reasonably well. Which means the algorithm is rarely what makes or breaks the app you choose. What does is everything around it: whether your data survives, whether the app respects your time, and whether you can see what is coming.

Here are the seven questions worth asking before you commit weeks of study to any app.

1. Does it use a proven, open scheduler?

The scheduler is the engine. Look for one that is a real memory model rather than a fixed multiplier, and that is open so its behaviour can be inspected. The current reference point is FSRS, the open, community-developed Free Spaced Repetition Scheduler — we explain how it works in our FSRS guide. A good scheduler also tells you the truth: when it says a card comes back in three weeks, it should mean three weeks, not a number rounded for comfort.

2. Will your data survive?

This is the question people skip and regret. Your deck represents hundreds of hours of thinking. Ask how the app syncs between your devices, what happens when two devices edit at once, and whether you can see the sync state at a glance. “It just syncs” is not an answer. You want sync that is loss-proof by design and transparent about what it is doing, so you never open the app to find last week’s cards gone.

3. Does it lock you out when you are done?

Many apps stop you once the day’s reviews are finished — “nothing due, come back tomorrow.” That sounds sensible and feels terrible when you have an exam in two weeks and an hour of free time right now. A well-designed app lets you study ahead when you want to, without breaking the schedule. Motivation is precious; an app should never be the thing that wastes it.

4. Can you see what is coming?

Spaced repetition front-loads work in a way that surprises people: skip a few days and the pile grows. The apps worth using make the future visible — a daily goal so you know what “done” means, a forecast of how many reviews are due on each coming day, and an activity calendar so you can see your own consistency. With that in view you can plan around a heavy week instead of being ambushed by it.

5. How do cards get made?

Making cards is where most study time actually goes, so this deserves scrutiny. Look for three routes: writing cards by hand in a proper editor (with images, tags and the option to reverse a card), turning your own material — a PDF, a scan, a web link, pasted text, even a dictated lecture — into cards, and drafting cards from a topic with AI. The quality question matters too: cards that capture a concept beat cards that capture a keyword, because a concept is what you will be asked to apply.

6. Is the pricing fair?

Read the pricing page as carefully as the feature list. Two things to check: whether the essentials — learning, the scheduler, writing your own cards and syncing them — are free without limits, and whether you are being pushed into a subscription you do not need. A fair model charges for what actually costs the maker something (AI generation, for example) and does it as a one-time purchase whose credits do not expire. If you cannot tell from the pricing page what you will pay in a year, that is itself the answer.

7. What happens to your privacy?

You will pour your study material — sometimes clinical cases, sometimes personal notes — into this app. Check what identity it requires and what it stores. Signing in with Apple, with the app storing neither your name nor your email, is the low-friction, low-exposure standard to look for.

How Repeto measures up

Repeto was built around exactly these seven questions. It schedules every card with the proven FSRS algorithm and shows honest intervals from one minute to months. Sync between iPhone and iPad is loss-proof and transparent. When your reviews are done, you may study ahead — Repeto never locks you out. The daily goal, streak, review forecast, activity calendar and card-maturity statistics keep the coming days visible. Cards come from an AI draft of a typed or dictated topic, from your own PDF, scan, web link, text or dictation, or from the editor with images, tags and reverse cards. The app, learning, scheduler, manual cards and sync are unlimited and free; only AI generation uses credits — a one-time purchase, around 100 cards free to start, and credits never expire. And you sign in with Apple; Repeto stores neither your name nor your email. See the full pricing on the home page.

Whatever app you pick, run it through these seven questions first. The right one will pass them without you having to squint.