Memly, an AI-powered learning app, now features the latest spaced repetition algorithm, FSRS 6.0, delivering a more efficient and personalized learning experience. In this article, we take an in-depth look at the learning revolution made possible by this groundbreaking combination.
What Is FSRS 6.0? The Latest Algorithm Built on the Science of Memory
FSRS (Free Spaced Repetition Scheduler) is an open-source spaced repetition algorithm that combines machine learning with insights from cognitive science. The latest version, FSRS 6.0, released in 2025, delivers performance that far surpasses all previous versions.
Background: Why FSRS Was Created
The traditional SM-2 algorithm (developed in 1987) has been used in many learning apps for nearly 40 years, but it suffered from a fundamental limitation: it did not leverage modern machine learning techniques.
FSRS was developed by Jarrett Ye (of MaiMemo Inc.) and achieves dramatic performance improvements by combining cutting-edge machine learning with insights derived from over 1.7 billion review records.
Five Revolutionary Features of FSRS 6.0
1. Fully Personalized Forgetting Curves
Traditional algorithms applied the same forgetting curve to every user. FSRS 6.0 introduces a new parameter (w20) that generates a forgetting curve unique to you.
- The w20 parameter is adjustable within a range of 0.1 to 0.8
- For most users, it optimizes to below 0.2
- For the first time, the shape of the forgetting curve differs for each individual
2. Dramatically Improved Same-Day Review Accuracy
The transition process from short-term to long-term memory is now modeled more scientifically. FSRS 6.0 accurately predicts the effect of multiple reviews on the same day and suggests optimal review timing.
- Parameters w17 and w18 control the impact of grades
- Parameter w19 adjusts the rate of stability change
- Good/Easy ratings are guaranteed not to decrease stability
3. Overwhelming Prediction Accuracy: 99.6% Superiority
In benchmark testing, FSRS 6.0 demonstrated superior memory prediction accuracy for 99.6% of users compared to the traditional SM-2 algorithm. Even compared to FSRS-5, improvements were confirmed for 88.2% of users.
4. Three-Dimensional Memory Management with the DSR Model
FSRS 6.0 manages memory through three independent components:
- Difficulty: Tracks the inherent difficulty of each card on a scale of 1 to 10
- Stability: The time it takes for memory retention to drop from 90% to 100%
- Retrievability: The probability of successful recall at the current moment
5. Adaptive Parameter Optimization
Twenty-one parameters are automatically adjusted based on your learning patterns. After more than 1,000 reviews, the optimization algorithm activates and generates a parameter set tailored specifically to you.
Why Memly Chose FSRS 6.0
By adopting FSRS 6.0, the number of reviews needed to achieve the same retention rate is reduced by 20-30%. On an annual basis, this translates to savings of hundreds of hours of study time.
- Prevention of over-studying: Eliminates unnecessary reviews and reduces learner burden
- Optimal timing: Places reviews just before forgetting occurs, maximizing memory retention
- Difficulty adjustment: Calculates the optimal interval individually for each card
Real-World Use Cases
Results in Language Learning
When mastering 10,000 English vocabulary words, the difference compared to traditional methods is striking:
| Metric | Traditional Method | FSRS 6.0 (Memly) |
|---|---|---|
| Time Required | 2 hours/day x 18 months | 1.5 hours/day x 12 months |
| Total Study Time | Approx. 1,080 hours | Approx. 540 hours |
| Time Reduction | - | Approx. 50% |
Application in Professional Exam Preparation
For professional certification exams such as bar exams and medical licensing exams, FSRS 6.0 is particularly effective in the following areas:
- Differentiated retention targets based on importance (e.g., constitutional law at 95%, commercial law at 85%)
- Efficient memorization of past exam question patterns
- Optimized comprehensive review during the final preparation period
Scientific Basis: The Evolution of the Forgetting Curve
FSRS 6.0 represents the culmination of approximately 140 years of memory research:
| Year | Model | Approach |
|---|---|---|
| 1885 | Ebbinghaus Forgetting Curve | Exponential function model |
| 2022 | FSRS v3 | Improved exponential function |
| 2023 | FSRS v4-5 | Transition to power function |
| 2025 | FSRS 6.0 | Personalizable power function |
The FSRS 6.0 formula is expressed as follows:
R(t,S) = (1 + t/(9xS))^(-1) x exp(-(t/(9xS))^w20)Here, w20 is the parameter that represents an individual's forgetting characteristics. This formula enables the evolution from a one-size-fits-all forgetting curve to one optimized for each individual.
Benchmark Results
These are the results of a large-scale validation using data from 20,000 Anki users:
| Algorithm | Log Loss | RMSE | Superiority over SM-2 |
|---|---|---|---|
| FSRS-6 | 0.30 | 0.052 | - |
| FSRS-5 | 0.33 | 0.058 | 88.2% |
| FSRS-4.5 | 0.34 | 0.061 | 92.1% |
| SM-2 | 0.41 | 0.089 | 99.6% |
Frequently Asked Questions
Is FSRS 6.0 really better than traditional methods?
Yes, it has been scientifically proven. A large-scale validation using data from 20,000 users showed that FSRS 6.0 outperforms the SM-2 algorithm in 99.6% of cases. On average, a 20-30% reduction in study time is achievable.
How much data is needed?
A minimum of 1,000 reviews is recommended for full optimization, but partial optimization is possible with as few as 400 reviews. Accuracy improves the more you use it.
Can it be used for short-term cramming?
Yes, it can. Special parameter sets are available for short-term learning, supporting intensive study sessions before exams. However, standard spaced repetition is recommended for building long-term memory.
Conclusion
The combination of Memly and FSRS 6.0 is not just an app update. It marks the beginning of a learning revolution that deeply understands human memory mechanisms and optimizes them with the latest technology.
From the old approach of "just keep repeating" to smart learning that "reviews at scientifically optimal times" -- this evolution will dramatically improve your learning efficiency, enabling you to acquire more knowledge, more reliably, in less time.
The FSRS development team is also considering more specialized versions, such as FSRS-F (which factors in fatigue) and FSRS-S (which specializes in short-term memory). Memly will continue to adopt these cutting-edge technologies as quickly as possible, delivering the best learning experience to our users.
For a comprehensive overview of AI-powered memorization support, see our article "What Is AI-Powered Memorization Support? A Complete Guide to How It Works, Its Effectiveness, and the Best Tools." To learn how AI flashcard apps use algorithms like FSRS, read How AI Flashcard Apps Work. For a direct comparison between Memly and Anki, see Memly vs Anki.