FSRS simulator
FSRS is the scheduler Anki uses to decide when you see a card again, and Bundle uses it too. Rate a card the way you would in a review and watch it pick the next date.
Imagine you’ve just seen this card for the first time. How well did you know it?
- STABILITY
- –days
- Set by your first rating
- DIFFICULTY
- –of 10
- Set by your first rating
- RECALL TODAY
- –
- Starts once you’ve seen it
Your memory curve starts with your first rating.
The short gaps a new card goes through on its first day, before FSRS schedules it in days.
Cards from what you read, scheduled with FSRS
Bundle asks you a few questions after every article you save and keeps the answers you want as cards. FSRS brings each one back just before you’d forget it.
What is FSRS?
FSRS stands for Free Spaced Repetition Scheduler. It’s an open-source algorithm, created by Jarrett Ye, that decides when you should see a flashcard again. Its default settings were fitted to hundreds of millions of real Anki reviews.
Anki has offered FSRS since version 23.10, and Bundle uses the current version, FSRS-6, for the cards you keep from what you read. It tries to show you each card just before you’d forget it. Every time you remember, the memory lasts longer, so the gaps grow from minutes to days to months.
Difficulty, stability and recall
FSRS keeps three numbers for every card, the same three the simulator shows.
- Difficulty
- How hard the card is for you, from 1 to 10. It goes up when you press Again or Hard, and down when you press Easy.
- Stability
- The number of days until your chance of recalling the card drops to 90%. If a card has a stability of 30 days, you’ll most likely still know it a month from now.
- Recall
- Your chance of remembering the card right now, which FSRS calls retrievability. It’s 100% just after a review and falls a little each day, quickly at first and then more slowly.
FSRS schedules the next review for the day recall falls to your desired retention.
Which desired retention to pick
Desired retention is the share of cards you want to still know when they come up. Anki’s default is 90%, and it’s a good place to start.
A higher number means more reviews. For a card with a stability of 11 days, FSRS waits 11 days at 90%, 4 days at 95% and 36 days at 80%. At 80% you review less, but you’ll forget about one card in five and have to learn it again.
If your reviews take too long each day, lower it a little. If you forget too many cards, raise it.
FSRS vs SM-2
SM-2 is the algorithm Anki used before FSRS, and it dates from 1987. Each card gets an ease, 250% to start, and each time you press Good, the last gap is multiplied by it. SM-2 has no estimate of how likely you are to remember the card.
FSRS estimates your chance of recalling each card and schedules the card for the day that chance falls to your desired retention. When you click Optimize in Anki, it fits its settings to your own review history. The Anki manual says this helps you remember more material in the same amount of time.
How to turn on FSRS in Anki
- Update Anki on your computer to version 23.10 or later.
- Click the gear next to any deck, then Options.
- Scroll down to FSRS and turn it on. It applies to all your decks.
- Set Desired retention, then click Optimize so FSRS fits its settings to your review history.
- Click Save. AnkiMobile and AnkiWeb pick up the change when you sync.
How Bundle uses FSRS
Bundle schedules your cards with FSRS-6, using its default settings and a desired retention of 90%.
You answer each card with Forgot or Remembered, which count as Again and Good. If you’d rather have all four buttons, pick Detailed under Answer buttons in Bundle’s review settings.
A new card, or one you forget, comes back once after 10 minutes. To try that in the simulator, pick Bundle under Learning steps.