Anki is a flashcard program built on 📝spaced repetition: it schedules each card's next review for when the learner is most likely to forget it. The free computer version runs on Windows, macOS and Linux. AnkiMobile is the official iOS app, and its purchases help fund Anki's development; AnkiDroid for Android is free and developed by contributors. The free AnkiWeb synchronization service keeps cards in step across devices.
Anki's manual credits 📝SuperMemo with pioneering the concept of a system that keeps track of the ideal time to review material, and states that Anki's spaced repetition system is based on SM-2, an older version of the SuperMemo algorithm. It adds that a newer algorithm, FSRS, has been integrated as an alternative to the legacy SM-2. The homepage describes Anki as a community project where anyone can contribute, including by helping maintain Anki or creating add-ons. Its source code is published on GitHub, where the license file states that Anki is licensed under the GNU Affero General Public License, version 3 or later, with portions contributed by users under the BSD-3 license. Anki is a registered trademark of Ankitects Pty Ltd.