FSRS4Anki

✨ A modern spaced-repetition scheduler for Anki based on the Free Spaced Repetition Scheduler algorithm ✨

Introduction
How to Get Started?
Add-on Compatibility
Contribute
- Contributors
Stargazers over time

Introduction

FSRS4Anki 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.

For details about the FSRS algorithm, please read the algorithm. If you are interested, you can also read my papers:

A Stochastic Shortest Path Algorithm for Optimizing Spaced Repetition Scheduling (free access), and
Optimizing Spaced Repetition Schedule by Capturing the Dynamics of Memory (submit a request).

FSRS4Anki 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 v23.10 or newer, refer to this tutorial.

If you are using an older version of Anki, refer to this tutorial.

Note that setting up FSRS is much easier in Anki v23.10 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
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`.
Learn Now & Grade Now	Yes ✅	`Learn Now` is compatible for Anki version 23.12. `Grade Now` works fine with the scheduler, but it doesn't work with `Compute optimal retention (experimental)`.
Incremental Reading v4.11.3 (unofficial clone)	No ❌	It shows the interval given by Anki's built-in scheduler, not the custom scheduler.
Auto Ease Factor	No ❌	The `Ease Factor` doesn't affect the interval given by FSRS. So, you won't benefit from using this add-on.
Delay siblings	No ❌	Delay siblings will modify the intervals given by FSRS. However, the FSRS4Anki Helper add-on has a similar feature that works better with FSRS. So, use the FSRS4Anki Helper add-on instead.
autoLapseNewInterval	No ❌	The `New Interval` doesn't affect the interval given by FSRS. So, you won't benefit from using this add-on.
Straight Reward	No ❌	The `Ease Factor` doesn't affect the interval given by FSRS. So, 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