FSRS spaced repetition algorithm
Hacker ApprovedSpaced repetition algorithm in Learning
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.
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.
17 people gave an opinion
- recommend it
- 16
- criticize it
- 1
- approval share
- 94%
Recommended in 7 of 13 months
- November 2025: not recommended
- December 2025: recommended
- January 2026: recommended
- February 2026: recommended
- March 2026: recommended
- April 2026: recommended
- May 2026: not recommended
- June 2026: not recommended
- July 2026: recommended
- August 2026: recommended
- September 2026: not recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it carries the badge
- 16 people recommend itNeeds 10 or more, met.
- 16 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 7 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Effective for memorizing vocabulary
“FSRS is much better. For me it was the difference between learning 10 new words of Mandarin a day and learning 20”
Comment from 3 Feb 2026 in “Ownership of open source flashcard app Anki transferred to for-profit AnkiHub” “FSRS is the best way to remember vocabulary”
Comment from 1 Aug 2026 in “Software for One” “memorizing is actually very easy with FSRS”
Comment from 10 Jul 2026 in “A Love Letter to Flashcards” Reduces review workload
“FSRS leads to an incredibly reduced workload.”
Comment from 3 Feb 2026 in “Ownership of open source flashcard app Anki transferred to for-profit AnkiHub” “memorizing is actually very easy with FSRS”
Comment from 10 Jul 2026 in “A Love Letter to Flashcards” Based on scientific research
“If the algorithm actually does the recall probability very well like FSRS does”
Comment from 14 Dec 2025 in “Hashcards: A plain-text spaced repetition system” “That one is actually based on scientific research”
Comment from 13 Jul 2026 in “A Love Letter to Flashcards”
What people warn about
Each mark is one comment
Some cards get absurdly long intervals
“intervals on some cards become absurdly large (4 years after seeing the card twice)”
Comment from 3 Feb 2026 in “Ownership of open source flashcard app Anki transferred to for-profit AnkiHub” “the modern algorithms like FSRS are actually almost too good at scheduling”
Comment from 24 Dec 2025 in “Spaced Repetition for Efficient Learning” Past refactor broke the API
“they had some refactor last year that broke the API”
Comment from 14 Mar 2026 in “Spaced Repetition Algorithm: A Three‐Day Journey from Novice to Expert”
What people said
15 of the 18 comments that mention it, newest first. Each links to the original comment.
“FSRS is the best way to remember vocabulary”
“That one is actually based on scientific research”
“memorizing is actually very easy with FSRS”
“It's a fantastic new-ish scheduler for spaced repetition”
“they had some refactor last year that broke the API”
“intervals on some cards become absurdly large (4 years after seeing the card twice)”
“FSRS is much better. For me it was the difference between learning 10 new words of Mandarin a day and learning 20”
“FSRS leads to an incredibly reduced workload.”
“FSRS just works, even without a GPU so it's not the cool kind of AI / machine learning these days.”
“I'm glad to hear that FSRS becomes more and more popular!”
“That sounds nearly perfect for FSRS”
“At least for me, they just failed. Thr fact is, they have no idea about when I am about to forget this or that fact.”
“the modern algorithms like FSRS are actually almost too good at scheduling”
“I think it's general consensus that moving from SM-2 to FSRS will show great improvement.”
“If the algorithm actually does the recall probability very well like FSRS does”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.