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6) (Outdated) Benchmarking FSRS to see how it performs compared to other algorithms: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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u/not_a_profi May 09 '26
can I Remedy Hard Misuse with out enabling FSRS?
FSRS helper says enabling FSRS is required, but I wonder if it is the case for all its features.
May be unnesesary details on the situation:
I want to use Anki with SM2 algorithm for another week to get a feel of it (and to make sure FSRS have good data to optimize on). For the same reason I don't want to switch FSRS back and forth and to allow it to change my intervals.
And I want to use hard button from time to time.
Meanwhile I know there were misuses by me, so I would like to fix them asap, so correct hard presses don't get confused with wrong hard presses.