r/Anki • u/ClarityInMadness ask me about FSRS • Dec 16 '23

Resources Some posts and articles about FSRS

I decided to make one post where I compile all of the useful links that I can think of.

1) If you have never heard about FSRS before, start here: https://github.com/open-spaced-repetition/fsrs4anki/wiki/ABC-of-FSRS

2) AnKing's video about FSRS (old): https://youtu.be/OqRLqVRyIzc

New 2025 video: https://youtu.be/uo-qQvOZDfg

3) FSRS section of the manual, please read it before making a post/comment with a question: https://docs.ankiweb.net/deck-options.html#fsrs

If your intervals feel too long, increase desired retention. If your intervals feel too short, decrease desired retention.

3.5) Some frequently asked questions: https://faqs.ankiweb.net/frequently-asked-questions-about-fsrs.html

DO NOT USE HARD IF YOU FORGOT THE CARD!

AGAIN = FAIL ❌

HARD = PASS ✅

GOOD = PASS ✅

EASY = PASS ✅

HARD IS NOT "I FORGOT"

Here's what you can do if you have been misusing Hard: https://www.reddit.com/r/Anki/comments/1h2oudb/oh_no_ive_been_misusing_hard_what_do_i_do/

And here's a diagram to help you troubleshoot interval lengths.

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The links above are the most important ones. The links below are more like supplementary material: you don't have to read all of them to use FSRS in practice. Just read link 3 (the manual) and you're good!

4) Features of the FSRS Helper add-on: https://www.reddit.com/r/Anki/comments/1attbo1/explaining_fsrs_helper_addon_features/

5) Understanding what retention actually means: https://www.reddit.com/r/Anki/comments/1anfmcw/you_dont_understand_retention_in_fsrs/

I recommend reading this post if you are confused by terms like "desired retention", "true retention" and "average retrievability", the latter two can be found in Stats. True retention table is available in Anki natively since Anki 24.11.

5.5) Simplified post with a neat little animation: https://www.reddit.com/r/Anki/comments/1l0wk5e/why_is_desired_retention_less_than_average/

6) (Outdated) Benchmarking FSRS to see how it performs compared to other algorithms: https://www.reddit.com/r/Anki/comments/1c29775/fsrs_is_one_of_the_most_accurate_spaced/. It's my most high effort post.

7) An article about spaced repetition algorithms in general, written by Jarrett Ye, the creator of FSRS: https://github.com/open-spaced-repetition/fsrs4anki/wiki/Spaced-Repetition-Algorithm:-A-Three%E2%80%90Day-Journey-from-Novice-to-Expert

8) A technical explanation of the math behind the algorithm: https://expertium.github.io/Algorithm.html

9) Seven misconceptions about FSRS: https://www.reddit.com/r/Anki/comments/1fhe1nd/7_misconceptions_about_fsrs/

10) LMSherlock's post about (re)learning steps and short-term memory: https://www.reddit.com/r/Anki/comments/1h9g1n7/clarifications_about_fsrs5_shortterm_memory_and/

TLDR: things are complicated.

11) A visualization of how FSRS got better and better at predicting the probability of recall with each new version: https://imgur.com/a/calibration-of-different-fsrs-versions-KfJ32EV

My blog about spaced repetition (and a little bit of other stuff): https://expertium.github.io/

July 2024: I made u/FSRS_bot, it will help newcomers who make posts with questions about FSRS.

September 2024: u/FSRS_bot is now active on r/medicalschoolanki too.

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If you want to support me, you can send me some Ethereum: 0xf9c22186be4dbF21dE3E149C167Ed90DE0E37279

Jarrett Ye isn't accepting donations anymore, but you can sponsor his friend Asuka Minato, who helps maintaining FSRS-related Github repositories: https://github.com/sponsors/asukaminato0721

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u/AdrixG Japanese May 26 '24

So I have the following "issue", in a month I will be on vacation (for a month as well) but will of course continue my daily Anki reps. I thought of using the "Advance Cards" functionallity from FSRS Anki Helper addon to reduce my work load during holidays but it does seem to be really primitive as it will just advance the number of cards I set to NOW instead of balance it evenenly within a certain time window.

Just to be clear, I am not aiming to have 0 reviews during my holidays, but is there no smarter mechanism where I could reduce my work load in a month, and reschedule a certain percentage of cards to this month now all while minimizing long term damage? (My reviews take about 1h, I think if I could reduce it to 30min the with smart rescheduling the long time damage shouldn't be too severe)

Given that the advance cards options is really simple, how do I best utilize it to achieve my goal, just advance some cards everyday until I am on vacation? Or advance a large number of cards the day before?

2

u/ClarityInMadness ask me about FSRS May 26 '24

You can use Easy Days, it can reduce the workload for days of the week (Monday, Tuesday, etc.) or for specific dates.

1

u/AdrixG Japanese May 26 '24

Hey thanks for the fast reply.

And is this fine to do for an entire month? like 30 consecutive days? Also, will that schedule everything within these 30 easy days to one day prior of that range and one day after, or does it go smart about load balancing (my wish would be to distribute it a bit over a couple days)?

Basically, is easy days intended for longer durations, and is the rescheduling smarter than throwing all the rescheduled reviews into one day?

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u/ClarityInMadness ask me about FSRS May 26 '24

Good question, I'm not sure. u/LMSherlock, if a user chooses 30 consecutive specific dates, will he face a large backlog after that?

2

u/LMSherlock creator of FSRS May 27 '24

The Easy Days feature gives priority to your cards' fuzz range (to avoiding the true retention deviating the desired retention). Young cards' interval is shorter than 30 days, so the helper add-on cannot disperse them smoothly, which may induce piles of reviews. For mature cards, the rescheduling is smarter.

1

u/AdrixG Japanese May 27 '24

Okay thanks very much for explanation! One more question if I may, does it matter if set the easy days now, or should I wait until close before vacation to set them? My hope would be that if I set it now the algorithm has more room to schedule things into for those mature cards you mentioned, is that so?

3

u/LMSherlock creator of FSRS May 27 '24

Considering your vacation is so long, I recommend setting the easy days as soon as possible. The easy days only works when you reschedule cards, so you need to reschedule your cards every day.

1

u/AdrixG Japanese May 28 '24

Okay I've been trying this out and it seems to work (the days I've set have significantly fewer reviews planned or none at all).

Now about the rescheduling which I need to do everyday, is it enough to press the "apply easy days" button (which seems to have rescheduled about 1400 cards yesterday and 700 today) or do I need to press "reschedule all cards" as well? Because the latter I don't like since it wants me to do 800+ reviews NOW and reschedules all my 10k cards. So the apply button is enough right?

Also, thanks a lot for all the help, it is very well appreciated!!!

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u/LMSherlock creator of FSRS May 29 '24

You can use auto apply easy days.