# FSRS spaced repetition algorithm

Hacker Approved page: https://hackerapproved.com/p/fsrs/

14 people recommended FSRS spaced repetition algorithm in Hacker News comments, 2 had mixed feelings and 1 criticized it, November 2025 to October 2026. It was recommended in 6 of 12 months, in 9 threads. It meets the Hacker Approved badge rule.

**Verdict:** Free open-source spaced repetition scheduler, used in Anki, that people say cuts review workload and helps memorize vocabulary. Critics note some cards get absurdly long intervals.

Summary written by Claude from 15 comments.

## Why people recommend it

- Effective for memorizing vocabulary (3 comments in the sample): "FSRS is much better. For me it was the difference between learning 10 new words of Mandarin a day and learning 20" ([source](https://news.ycombinator.com/item?id=46867608)) "FSRS is the best way to remember vocabulary" ([source](https://news.ycombinator.com/item?id=49139256)) "memorizing is actually very easy with FSRS" ([source](https://news.ycombinator.com/item?id=48863480))
- Based on scientific research (2 comments in the sample): "If the algorithm actually does the recall probability very well like FSRS does" ([source](https://news.ycombinator.com/item?id=46267466)) "That one is actually based on scientific research" ([source](https://news.ycombinator.com/item?id=48892464))
- Reduces review workload (1 comment in the sample): "FSRS leads to an incredibly reduced workload." ([source](https://news.ycombinator.com/item?id=46866632))

## What people warn about

- Some cards get absurdly long intervals (2 comments in the sample): "intervals on some cards become absurdly large (4 years after seeing the card twice" ([source](https://news.ycombinator.com/item?id=46868063)) "the modern algorithms like FSRS are actually almost too good at scheduling" ([source](https://news.ycombinator.com/item?id=46379749))
- Past refactor broke the API (1 comment in the sample): "they had some refactor last year that broke the API" ([source](https://news.ycombinator.com/item?id=47376726))

## The badge

A product earns the Hacker Approved badge when at least 10 people recommend it, recommenders outnumber critics at least 2 to 1 (mixed feelings count toward neither side), it was recommended in at least 4 of the 12 months and in at least 5 different threads, and no single thread supplies more than half of the people who recommend it. Health and money products are never badged.

## Cite as

Hacker Approved, "FSRS spaced repetition algorithm", https://hackerapproved.com/p/fsrs/ (14 recommend, 2 mixed, 1 criticize; Hacker News comments, November 2025 to October 2026).

Counts updated 2 Nov 2026, with data through October 31, 2026.