Smart scheduling
FSRS, explained simply
Reviewing a word you still remember wastes time. Reviewing it after you have forgotten it wastes the learning. FSRS is the algorithm that aims between the two — for every word, from your own answers — and in Rayaad it is on from your first card, with nothing to set up.
- Two answers, not a four-point scale
- No intervals to choose and no settings to tune
- The same schedule on every device
What it does
Each right answer stretches the wait
The chart above is Rayaad’s real schedule for a word you keep getting right: tomorrow, then a few days, then weeks, then months. After eight correct answers the word is 11 months away. To do that, FSRS keeps track of three things for every card.
Retrievability
How likely you are to remember the word right now. It falls over time, and the word comes back as it nears the target.
Stability
How slowly that memory fades. Every correct answer makes it more durable, which is why the gaps keep growing.
Difficulty
How stubborn this word is for you. Two words reviewed equally often get different gaps if one keeps catching you out.
Getting it wrong
A miss is a correction, not a punishment
Swipe “Didn’t know” and the word comes back in about a minute, after a few other cards, so you recall it rather than read it off the screen.
It does not throw away what you had built. On a word four answers in, its memory estimate drops from about 48 days to about 3 — reduced, not reset — and once you get it right it is next due tomorrow.
- 19 days awayFour correct answers in. You meet the word and blank.
- Back in about a minuteYou swipe “Didn’t know”. It returns in the same session.
- Next tomorrowYou get it. Not back to day one — back to where it can climb.
Compared
Why not a fixed schedule?
“One day, three days, a week, a month” is easy to explain and wrong in both directions: it shows you words you already know well, and words you are about to lose too late.
| Fixed intervals | SM-2 | FSRS | |
|---|---|---|---|
| What sets the gap | The same ladder for every word | One “ease” number per card, multiplied | A model of each word’s memory, updated every answer |
| Hard words | Treated like easy ones | Ease shrinks, and can get stuck low | Difficulty is tracked separately from how long you have known it |
| After a break | No idea what to do | Picks up where it left off | Knows how long it has really been, and adjusts |
Beyond the label
What a good FSRS app gets right
Plenty of apps list FSRS as a feature. Four questions separate a real implementation from a checkbox — here are Rayaad’s answers.
Is it on by default?
An opt-in scheduler is one most people never switch on. Rayaad has no other scheduler: nothing to enable, nothing to turn off.
Are the settings published?
Rayaad’s are, in the table below: FSRS-6, 95% target retention, one-minute learning steps and the full parameter set.
Do your devices agree?
The server replays each card’s full history through the same scheduler, so a phone, a browser and an extension never drift apart.
Is your history kept?
Every answer is stored permanently with the scheduler version that produced it, so a schedule stays explainable even after a change.
Exactly what Rayaad ships
The settings, published
Read straight from the configuration file the app and the server both schedule with. If it changes, this table changes with it.
| Setting | Value | What it means |
|---|---|---|
| Algorithm | FSRS-6 | The current generation of FSRS, via [email protected]. |
| Target retention | 95% | How likely you should be to remember a card at the moment it comes back. |
| Learning steps | 1m / 1m | One short step for new and missed cards, then straight into real intervals. |
| Interval fuzz | Off | The same history always gives the same schedule, so it can be checked. |
| Longest interval | 36,500 days | Effectively no ceiling. A word you truly know stops costing you anything. |
| Retry floor | 90s, 5 cards | A missed card waits for other cards to pass before it can come back. |
| Scheduler version | fsrs-6-ts-fsrs-5.4.1-rayaad-v2 | Stored with every review you make. |
New to the idea? Start with what spaced repetition is, or see what a review looks like.
FSRS questions
What does FSRS stand for?
Free Spaced Repetition Scheduler. It is an open-source algorithm that decides when each flashcard should come back, built from research on how memory fades, and it is used by a growing number of serious review apps.
How is FSRS different from SM-2?
SM-2, the older algorithm many apps still use, keeps one "ease" number per card and multiplies the interval by it. FSRS models three things instead: how likely you are to remember the card right now, how durable the memory is, and how hard the card is for you. Separating durability from difficulty is why it schedules more accurately.
Do I have to configure anything?
No. Rayaad ships one tuned set of parameters and has no scheduling settings to adjust. The exact configuration is published below and stored with every review as fsrs-6-ts-fsrs-5.4.1-rayaad-v2.
Does FSRS work with only two answers?
Yes. FSRS works correctly when only "again" and "good" are used — it is a supported way to use it, not a lesser one. Rayaad’s two answers map to exactly those.
What retention does Rayaad aim for?
95%: the chance, at the moment a card comes back, that you still remember it. Aiming higher means more reviews; aiming lower means more forgetting.
What happens if I stop for a month?
Nothing is lost and nothing is punished. Words that came due while you were away are simply due. The ones you have forgotten go back to short gaps, and the ones that stuck keep their long ones.
Let the scheduling run itself
Add a few words and see the gaps grow. Free to start, with nothing to configure.