When/How to separate presets for FSRS

I started to use anki by importing cards from SM, no repetition history, and using FSRS from the beginning with default parameters. I have 3 decks with > 400 reviews , another few with close to 400 each, and the remaining 7 decks have around 600 reviews total (I don’t think there is a way to export a graph showing distribution of reviews by deck), also some decks I haven’t used yet.

I have a single preset for all 30 decks. I believe I used the “Optimize” button only once, when it was recommended to be done by all users due to an upgrade in the anki version.

How do I determine how many presets to have, for the purposes of FSRS, and which combination of decks to combine into which presets? Eg, if I am looking into statistics per deck, what exactly am I looking for?

Or is it recommended to run this code (when I figure out how to do it), and what do I look for in those results?:

Version ⁨24.04.1 (ccd9ca1a)⁩

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That code is experimental, forget about it.
Separating material into presets is subjective. If you feel like the material is different - make a different preset.
Also, please read this: fsrs4anki/docs/tutorial.md at main · open-spaced-repetition/fsrs4anki · GitHub

A better person to ask this is L.M.Sherlock the man himself.

As for the main concern, here is what Sherlock says,

I haven’t found out an objective method. Here is an initial experiment: GitHub - open-spaced-repetition/fsrs-when-to-separate-presets

I say this thing a lot but it always blows me up to think how similar most humans think because that’s the same question I asked Sherlock. Here’s the issue: [Question]: Questions regarding Optimisation · Issue #646 · open-spaced-repetition/fsrs4anki · GitHub

Edit: But @Expertium saying it’s “subjective” generally means the truth depends upon who is being asked. Here, even though the impression maybe of subjectivity there must lie undiscovered objective standards.

I saw, that but it just says

If you have decks that vary wildly in difficulty, it is recommended to use separate presets for them because the parameters for easy decks and hard decks will be different.

In Card Difficulty under stats, would I just look at “average difficulty” for each deck (and maybe combine decks with similar ones for now into one preset), or maybe what the distribution of difficulty looks like?

It means subjective difficulty, not FSRS difficulty. I don’t know how to word that better. Suggestions are welcome.

that’s the best way to phrase it IMO. Expertium’s saying go with your guts.

But, one more thing, and I’m calling this pattern of learning. Say in Maths, you need to practice the same thing again and again, but then once learned the memory becomes very stable. This is different with vocabulary because there’s no “understanding” part. S partly it will depend upon the essence or the nature of the material.

Edit: btw saying difficulty might confuse people because often the same type of material has different difficulty levels. Different cards will feel different etcetra.


  • if all cards in a subdeck with many review cards have a 60% FSRS difficulty, then the cards in the other subdecks vary too much for a preset that would work best for this subdeck (assuming its difficulty is not actually that uniform).
  • I think Sherlock said that cards with 0% or 100% FSRS difficulty are scheduled worse than others.
  1. The FSRS difficulty is relative. You cannot compare two cards’ difficulty unless they are in the same preset.
  2. I haven’t said that. Actually, FSRS has good performance in cards with high difficulty:



I meant in the same preset (because this topic about separating).

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I think the graph above shows that it performs well enough for those cards.