Stability
How many days until your chance of recalling the word drops to 90%. This is the gap FSRS aims for, so it grows with every successful review.
The scheduler behind FlashLoop
When does a word come back? FSRS decides.
FlashLoop schedules reviews with FSRS, the Free Spaced Repetition Scheduler — the open-source algorithm that is also built into Anki. It keeps a model of your memory for every word and brings the word back right before you would forget it.
Last review 10 days agoDue today
figure out
understand · solve
- Stability
- 11 days
- Difficulty
- 2.1 / 10
- Recall now
- 91%
Each button shows its next date before you press it.
01 · The forgetting curve
Review at the edge of forgetting.
Right after a review you are almost sure to remember a word. Then the chance slowly drops. FSRS brings the word back when that chance falls to 90%: early enough that you still recall it, late enough that recalling it takes a little effort.
That effort is the point. Each successful recall makes the memory more durable, so the curve gets flatter and the next gap gets longer.
| Day | After the 1st review | After the 2nd review | After the 3rd review |
|---|---|---|---|
| 1 | 94% | 99% | 100% |
| 2 | 90% | 97% | 99% |
| 7 | 79% | 92% | 98% |
| 10 | 76% | 90% | 97% |
| 30 | 65% | 81% | 92% |
| 44 | 62% | 77% | 90% |
| 60 | 59% | 74% | 88% |
02 · What FSRS tracks
Three numbers for every word.
Every answer you give updates them. Nothing is a fixed table like “Good = 7 days”: the same button gives a different gap for different words.
Difficulty
From 1 to 10: how hard this word is for you. Again and Hard push it up, Easy brings it down. The higher it is, the slower stability grows.
Recall chance
The chance you would remember the word right now. 100% just after a review, 90% on the day it is due, lower if you come back late.
03 · A word’s journey
Gaps grow fast when you keep remembering.
Here is one word, answered Good every time it was due. Two days, then ten, then six weeks. By the fifth review the word is safe for well over a year — and you spent five short reviews on it.
That is why FSRS feels light: time goes to the words you are about to lose, not to the ones you already know.
2 d1st
10 d2nd
44 d3rd
159 d4th
503 d5th
04 · The four buttons
Grade what happened, not what you want.
The buttons describe how the recall went. FSRS turns that into a date — you do not have to think about intervals at all.
05 · The most common mistake
Hard is not “I forgot”.
Hard is a pass. When you press it, FSRS hears “I still remembered this after 10 days”. That is good news about your memory, so the gap grows — just less than it would with Good.
Only Again makes the next gap shorter. If a word slipped, press Again: it comes back in 10 minutes and starts over with short gaps.
Pressing Hard on words you actually forgot is the habit Anki users call “Hard misuse”: FSRS keeps believing you remember them, and every gap stretches.
The same word, 10 days after its last review
10 min
31 d
44 d
72 d
06 · What it costs
Hard slows a word down. Again sends it back.
Four ways the same word can go. Hard does not undo progress, but it raises the word’s difficulty, so every later gap grows more slowly. Again starts the gaps over from short ones — exactly what a word you forgot needs.
Good every time
Difficulty stays at 2.1Hard once
Difficulty 2.1 → 4.7Hard twice
Difficulty 2.1 → 6.5Forgot once
Difficulty 2.1 → 7.4Each pill is one answer and the gap it scheduled. Answers given on the day the word was due.
07 · New words
A short step first, then FSRS takes over.
A word you have never answered starts with one short step. Again and Hard keep it in today’s session; Good or Easy hand it to FSRS.
- While a word is still in its first step, Hard just means “show it again” and does not count as long-term progress.
- A word you had to repeat today comes back tomorrow after Good, not in a week.
- Dates get a little random spread, so words added together do not come back in one clump forever.
A brand-new word
FSRSThe first answer
Forgot a word you knew?One 10-minute look, then FSRS rebuilds the gaps from a shorter start.
Questions
Good to know.
I pressed Hard. Why is the next review further away than the last one?
Because Hard means you remembered. You recalled the word after a long gap, so your memory of it is stronger than FSRS thought, and the gap grows. Hard grows it less than Good and raises the word’s difficulty. If the word had actually slipped, press Again.
What if I skip a day, or a week?
Nothing resets. Due words wait in your queue, and FSRS uses the real time that passed. If you still remember a word after a longer gap than planned, that is strong evidence, and the next gap grows more: a word due after 10 days and answered Good after 20 comes back in about 62 days instead of 44.
Why does a new word wait 2 days after Good, not one?
A brand-new word gets one short step: Again brings it back in a minute, Hard in two. Good graduates it, and FSRS’s starting estimate for a word you got right on the first try is about two days. A word you needed to repeat today comes back tomorrow at most.
Why 90%?
It is the balance most learners settle on. Aiming for 95% would cut every gap to about 40% of its length and roughly double your reviews; aiming lower saves time but lets more words slip.
Is this the same FSRS as in Anki?
Yes, the same algorithm: FlashLoop runs the open-source ts-fsrs implementation of FSRS-6 with its default parameters. The dates under the buttons are computed by the same code that saves your answer, so what you see is what you get.
Rate honestly, FSRS does the rest
Spend your time on the words you are about to lose.
FlashLoop is free: fresh AI sentences for every review, feedback on your answers and FSRS scheduling across web and Android.