Choosing one
A spaced repetition app is only as good as its intervals
Every tool in this category shows you cards. What separates them is when — and whether they will tell you how that was decided. Here is what Rayaad's scheduler actually does with a word you keep getting right.
The checklist
Six questions to ask any of them
Including this one. Each answer below is Rayaad's; the questions are the point, and they work just as well on the tool you are currently using.
- 1
Which algorithm does it use, and can you find out?
An app that will not tell you how it schedules is asking you to trust an interval you cannot check. FSRS is the current state of the art and is open; SM-2 is the older approach most tools inherited.
FSRS-6, with the exact parameter set published on the FSRS page.
- 2
Is there a daily review cap?
Spacing only works if a card is seen on the day it comes due. A cap on reviews — free tier or otherwise — breaks the mechanism rather than limiting it.
No cap, on any plan, and the free tier is where that promise matters.
- 3
How many answers does a card take?
Every extra option is a decision multiplied by hundreds of cards a week. Some people want the precision; most people want to be finished.
Two — knew it, or did not — plus undo.
- 4
Does it work offline?
The sessions you actually complete happen on trains, in queues and in bed. An app that needs a connection loses those.
Fully. Answers are written locally and pushed when there is a connection.
- 5
Can you get your material out?
A review history is years of work. An app you cannot leave is one you should think hard about entering.
One file with every card and every review, on any plan, at any time.
- 6
What happens when you stop for a month?
Life interrupts. A tool that punishes the gap — with a streak, with a backlog it presents as failure — is one you will not come back to.
The due pile is just due. No streak to break, and forgotten cards return to short intervals on their own.
The idea, in one paragraph
Anything you learn starts fading immediately, and the fade is not linear — each successful recall makes the next one last longer. Spaced repetition is the practice of arranging reviews to land near the moment of forgetting, because a review there does far more work than a review of something you still remember perfectly well. The hard part is knowing where that moment is for each item, which is what a scheduler is for.
Why the algorithm is the whole product
Two apps showing you the same cards with different intervals are not two versions of the same experience — one of them is wasting your time and the other is losing your words. A fixed ladder (one day, three days, a week, a month) treats a word you find trivial and one you keep missing identically. FSRS models each card's durability and difficulty separately, updates both on every answer, and targets a recall probability rather than a step number.
What "good" looks like in practice
- Intervals that reach months and years, so mature material stops costing you anything.
- A missed card that returns inside the same session rather than tomorrow.
- A visible due count before you start, so a session has an end.
- The same schedule on every device, computed from your full history rather than from whichever device synced last.
Rayaad does all four. A card answered correctly eight times will not be back for 11 months — see exactly how that is calculated, or how other tools handle it.
About spaced repetition
What is a spaced repetition app?
A tool that decides when to show you each thing you are trying to remember, based on how likely you are to have forgotten it. Rather than reviewing everything on a fixed cycle, it spaces each item individually and lengthens the gap every time you recall it successfully.
Does spaced repetition actually work?
The underlying effect — that spacing your practice out beats massing it together, and that retrieving something is worth more than re-reading it — is one of the most consistently reproduced findings in learning research. What varies between tools is how well they estimate the right gap for each item.
How long should a daily session be?
It is set by what is due, not by a target you pick, and it settles at a level driven by how much you are adding rather than by how much you have learned. A mature deck of a few hundred words is usually a few minutes.
Is Rayaad a general-purpose spaced repetition app?
It schedules vocabulary in a language pair, with one card shape — and that focus is the point. A tool that only has to handle words can ship with its scheduler already tuned and nothing to configure, which is what makes a first session possible in under a minute.
Twenty words tonight.
Free plan with no review limit, on every device. No ads, and your words stay yours.