Anki's Algorithm: Damien Elmes's Flashcards, FSRS and Medical Students

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In 2010 Roger Craig broke the Jeopardy single-day winnings record using free software built to help people learn Japanese. That program, Anki, whose name means memorization in Japanese, was created on October 5, 2006, by Australian programmer Damien Elmes to study the language. It combines active recall with spaced repetition, scheduling each review just before a memory fades. For years it ran on a modified version of the SM-2 algorithm, created in the late 1980s by Piotr Wozniak for SuperMemo, using ease factors and simplifying SuperMemo's six-point grading to four buttons. An attempt to adopt SM-5 was abandoned after harder cards appeared to get longer intervals, a result Wozniak disputed and that Elmes later attributed to a likely implementation bug.

In October 2023, Anki 23.10 added an optional scheduler called FSRS, the Free Spaced Repetition Scheduler, which models difficulty, stability and retrievability and was trained on about 727 million reviews from 10,000 users. Benchmarks show it reaches the same retention as SM-2 with fewer daily reviews. The episode explains Anki's notes and card templates, cloze deletion, the free desktop and Android apps, the paid iOS app that funds development, and the 2026 handover of operations to AnkiHub. It closes on medicine, where the tool has become an unofficial curriculum.

• One note can generate several cards, such as English to French, audio to spelling, and French to English.
• The Android app, AnkiDroid, was created by a different developer, Nicolas Raoul, and is licensed under GPLv3.
• The community has built more than 1,600 add-ons, including image occlusion for anatomy diagrams.
• A 2024 study found 86.2 percent of U.S. medical students use Anki and 66.5 percent use it daily.
• A 2015 Washington University study found about one extra USMLE Step 1 point for every 1,700 unique cards studied, and the AnKing deck passed 300,000 downloads by 2024.