HackerReposA FIELD GUIDE TO OPEN SOURCE
ProSponsor the shelf♧ 0
← Back to top all-time
open-spaced-repetition
fsrs4anki
Jupyter Notebook2022–2026
open-spaced-repetition / fsrs4anki

fsrs4anki

A modern Anki custom scheduling based on Free Spaced Repetition Scheduler algorithm

28Distinct people
33Mentions
1Explicit recommenders
4.1KGitHub stars
REPOSITORY AT A GLANCE

What to know before exploring

What it is

A modern Anki custom scheduling based on Free Spaced Repetition Scheduler algorithm

GitHub

Where it is used

No documented product use was verified in the last source check.

What people are saying

I recommend the new algorithm of Anki: https://github.com/open-spaced-repetition/fsrs4anki

jarrett-ye used a recommendation phrase. One indexed comment matches. This is a phrase match, not a verdict.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

No other repository is repeatedly linked in the same discussions.

This week on Hacker News

Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 5:04:57 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year33 dated mentions

Observed mentions: 2022-12-27 22:27:30 UTC to 2026-03-13 23:53:52 UTC.

0510152022-01-01 00:00:00 UTC to 2023-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments20222023-01-01 00:00:00 UTC to 2024-01-01 00:00:00 UTC (exclusive): 4 mentions; 1 submissions, 3 comments2024-01-01 00:00:00 UTC to 2025-01-01 00:00:00 UTC (exclusive): 15 mentions; 3 submissions, 12 comments20242025-01-01 00:00:00 UTC to 2026-01-01 00:00:00 UTC (exclusive): 10 mentions; 2 submissions, 8 comments2026-01-01 00:00:00 UTC to 2027-01-01 00:00:00 UTC (exclusive): 3 mentions; 1 submissions, 2 comments. Incomplete calendar period.2026*

* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20222022-01-01 00:00:00 UTC2023-01-01 00:00:00 UTC101
20232023-01-01 00:00:00 UTC2024-01-01 00:00:00 UTC413
20242024-01-01 00:00:00 UTC2025-01-01 00:00:00 UTC15312
20252025-01-01 00:00:00 UTC2026-01-01 00:00:00 UTC1028
2026 (partial)2026-01-01 00:00:00 UTC2027-01-01 00:00:00 UTC312

From the project README

An excerpt from the repository, fetched Nov 13, 2026.

Read the project’s introduction
FSRS4Anki ✨ A modern spaced-repetition scheduler for Anki based on the Free Spaced Repetition Scheduler algorithm ✨ Table of contents Introduction How to Get Started? Add-on Compatibility Contribute Contributors Developer Resources Stargazers Over Time Acknowledgements Introduction FSRS4Anki (Free Spaced Repetition Scheduler for Anki) consists of two main parts: the scheduler and the optimizer. The scheduler replaces Anki's built-in scheduler and schedules the cards according to the FSRS algorithm. The optimizer uses machine learning to learn your memory patterns and finds parameters that best fit your review history. For details about the working of the optimizer, please read the mechanism of optimization. Research on the FSRS algorithm follows the path pioneered by Maimemo: data-driven, balancing interpretability and verifiability. See also: Maimemo: A Stochastic Shortest Path Algorithm for Optimizing Spaced Repetition Scheduling (free access) [中文版], and Maimemo: Optimizing Spaced Repetition Schedule by Capturing the Dynamics of Memory (Google Scholar) [中文版]. FSRS Helper is an Anki add-on that complements the FSRS4Anki Scheduler. You can read about it here: https://github.com/open-spaced-repetition/fsrs4anki-helper How to Get Started? If you are using Anki 23.10 or newer, refer to this section of the Anki manual. If you are using an older version of Anki, refer to this tutorial. Note that setting up FSRS is much easier in Anki 23.10 or newer. Add-on Compatibility Some add-ons can cause conflicts with FSRS. As a general rule of thumb, if an add-on affects a card's intervals, it shouldn't be used with FSRS. Add-on Compatible? Comment Review Heatmap Yes ✅ Doesn't affect anything FSRS-related. Advanced Browser Yes ✅ Please use the latest version. Advanced Review Bottom Bar Yes ✅ Please use the latest version. The KING of Button Add-ons Yes ✅ Please use the latest version. Pass/Fail Yes ✅ Pass is the equivalent of Good, Fail is the equivalent of Again. AJT Card Management Yes ✅ Compatible with Anki 23.12 and newer. Incremental Reading v4.11.3 (unofficial clone) Unsure ❓ If you are using the standalone version of FSRS, it shows the interval given by Anki's built-in scheduler, not the custom scheduler. This add-on is technically compatible with built-in FSRS, but FSRS was not designed for incremental reading, and FSRS settings do not apply to IR cards because they work in a different way compared to other card types. Delay siblings No ❌ Delay siblings will modify the intervals given by FSRS. However, the FSRS Helper add-on has a similar feature that works better with FSRS. Please use the FSRS Helper add-on instead. Auto Ease Factor No ❌ The Ease Factor is no longer relevant when FSRS is enabled, therefore you won't benefit from using this add-on. autoLapseNewInterval No ❌ The New Interval setting is no longer relevant when FSRS is enabled, therefore you won't benefit from using this add-on. Straight Reward No ❌ The Ease Factor is no longer relevant when FSRS is enabled, therefore you won't benefit from using this add-on. Let me know via issues if you want me to check compatibility between FSRS and some add-on. Contribute You can contribute to FSRS4Anki by beta testing, submitting code, or sharing your data. If you want to share your data with me, please fill out this form: https://forms.gle/KaojsBbhMCytaA7h8 Contributors Expertium ⚠️ 📖 🔣 🤔 🐛 user1823 ⚠️ 📖 🔣 🤔 🐛 Christos Longros 🔣 🖋 Developer Resources If you're a developer considering using the FSRS algorithm in your own projects, we've curated some valuable resources for you. Check out the Awesome FSRS repository, where you'll find: FSRS implementations in various programming languages Related papers and research Example applications using FSRS Other algorithms and resources related to spaced repetition systems This carefully curated list will help you better understand FSRS and choose the right implementation for your project. We encourage you to explore these resources and consider contributing to the FSRS ecosystem. Research Resources For those new to spaced repetition algorithms, we recommend starting with our comprehensive guide: Spaced Repetition Algorithm: A Three-Day Journey from Novice to Expert Dive deeper into the academic foundations of FSRS and spaced repetition through our curated collection of Datasets, Code & Research Papers Explore our extensive collection of Research Notebooks documenting detailed analyses and experiments with FSRS and spaced repetition algorithms Stargazers Over Time Acknowledgements A special thanks to 墨墨背单词 (MaiMemo) for their support of FSRS development by allowing its research engineer, Jarrett Ye, to dedicate part of his working hours to this open-source project. This greatly helps in the continuous improvement and maintenance of FSRS for the benefit of the entire community. We would also like to extend our sincere gratitude to Damien Elmes of Ankitects for his invaluable technical support, and to the AnkiWeb users for the review history dataset. Without their collective contribution, FSRS would not have achieved its current level of popularity and influence.
Read the full README on GitHub

What Hacker News says

33 sources
I found it a little annoying that SRS is immediately explained to mean Spaced Repetition System, but then the F is added without explaining what it stands for. Most references of the article do neither. Except https://github.com/open-spaced-repetition/fsrs4anki/wiki/The... which says the F means Free. Seems a little too easy? I found nothing else. Chatgpt says it means Flexible, which actually makes more sense? Anybody else can chip in?
In Spaced repetition systems have gotten better
My tip is to map the 1-4 difficulties as "wrong, or <60% confidence", "60-80% confidence, thought required", "90%+ confidence, thought required", and "90%+ confidence, no serious thought". Depending on what you're learning, you might vary those. For language learning, that works well imo. Also, make sure to switch to FSRS. The old algorithm defaulted to "again" resetting a card to 0, while "again" in FSRS does show it again, but doesn't reset it back to being effectively new. If you want to understand the algorithm, read this: https://github.com/open-spaced-repetition/fsrs4anki/wiki/ABC...
In Spaced repetition systems have gotten way better
I'm doing the same kind of thing for my college classes no matter the subject. But mine is a little different. Instead I do: 1. Feed lecture slides, labs, homework into ChatGPT and have it generate flashcards. 2. Write these flashcards into Anki and study them using Anki. 3. Run through some practice problems I had originally intended for this system to be used long-term, but I get irresponsible and study the day of the exam. It really depends on the material, but for the most part, it takes around 5–7 hours of studying and preparation to feel completely confident about the exam. Often times, I wake up super early on the exam day to give me some time. This is not ideal of course and is just a product of my bad habits. It's definitely doable to ace exams with only 2–3 of studying, but usually I need to pad it with another 2–3 hours of prep
Read the rest
aration like creating high quality flash cards and stuff. I believe most people can adopt this system and perform very well, but at the same time it's a very radical departure from traditional study practices and even then I'm not even using this system in the way it's actually intended (not the day of cramming-style method). This system is not something I made up, but rather backed from a collective community effort that has produced amazing techniques, guides, research, etc.: https://isaak.net/mandarinmethods/ - in depth guide detailing best practices with Anki regarding language learning (THE BEST) https://cademcniven.com/posts/20211119/ - recommended number of cards per day to study based on some grassroots research https://github.com/open-spaced-repetition/fsrs4anki - the most modern spaced repetition algorithm which uses machine learning to optimize for each individual's learning capabilities (THE BEST) https://www.reddit.com/r/Anki/comments/18jvyun/some_posts_an... - meta resource on fsrs https://www.justinmath.com/individualized-spaced-repetition-... - a reading which i've incorporated into the way i create flash cards pertaining to more problem-solving type of learning as opposed to pure memorization like facts about history https://thehardway.guide/ - a damn good book teaching about actionable and pragmatic advice about language learning that i've applied to all of my college courses
In How I Ace Midterms at a Top CS School by Studying 1-3 Hours (and Skipping Class)
My work is MIT, as is ts-fsrs. I said anki source code, but I was being hyperbolic. To understand the different exports of ts-fsrs I had to browse around in different repos at https://github.com/open-spaced-repetition (particularly rs-fsrs; which I think is used in Anki proper) as well as read the algorithm https://github.com/open-spaced-repetition/fsrs4anki/wiki/The... and infer by names being used. I complain here, but this is open source and if I was slightly more ambitious I would submit PR with the missing docs (or at least an issue). PS. my work is here https://github.com/runarberg/shodoku in case you are interested, but the source code bears the mark of being a weekend hobby project, so read at own risk ;)
In Spaced repetition can allow for infinite recall (2022)

Showing the 15 most recent of 33 sources. Enable JavaScript to search and browse every indexed mention.

MAKE YOURSELF AT HOME

A few shortcuts

/
Search the collection
?
Open this guide
Esc
Close dialogs and navigation

Your saved repositories and interests stay in this browser.