Anki
The open-source spaced-repetition flashcard system researchers trust.
About
Anki is a free, open-source flashcard program built around active recall and spaced repetition, maintained by Ankitects Pty Ltd with community contributors. Its scheduler — the classic SM-2 algorithm plus the newer FSRS scheduler, which optimizes scheduling parameters from your own review history — shows you each card at roughly the moment you would otherwise forget it, cutting review load while preserving retention. Cards support text, images, audio, video, and LaTeX-rendered math, with flexible note types including basic, reversed, type-in-the-answer, cloze deletion, and image occlusion, and one note can generate multiple cards.
Decks sync across devices through the free AnkiWeb service (advanced users can run their own sync server), collections handle 100,000+ cards, and a large add-on ecosystem extends the interface and scheduling. Thousands of community shared decks cover medicine (AnKing, Zanki), languages, and law. It is free on desktop, Android (AnkiDroid), and web; the official iOS app is a one-time $24.99 purchase that funds development. The desktop codebase is AGPL-3.0 with roughly 32,000 GitHub stars, and two decades of use across medical schools and language learners make its scheduling the most battle-tested in the category. Tradeoffs: the interface is dated with a steep learning curve, card creation is largely manual, and review queues can become overwhelming without discipline.
What it can do
- Spaced repetition with SM-2 and FSRS (self-optimizing) schedulers
- Flexible note types: basic, reversed, cloze deletion, image occlusion, type-in-the-answer
- Media support: images, audio, video, LaTeX math
- Handles 100,000+ card decks smoothly
- Free sync across devices via AnkiWeb; self-hostable sync server
- Thousands of shared community decks (medicine, languages, law)
- Large add-on ecosystem for interface and scheduling extensions
- Detailed statistics on reviews, retention, and scheduling
- Automatic collection backups
- AGPL-3.0, ~32k GitHub stars, 20+ years of development
Setup
Download Anki free for Windows, macOS, or Linux from apps.ankiweb.net, or AnkiDroid free on Android. Create a free AnkiWeb account to sync decks and progress across devices. Build your own decks or import shared decks from AnkiWeb; iOS users can buy the $24.99 AnkiMobile app or use the free web version.
Prerequisites
A desktop, Android, or iOS device; an AnkiWeb account only for sync.
Use cases
Works with
Trust score — 9/10
Scored 9/10 (verified tier, metrics-v1). Evidence: ~32.1k GitHub stars with commits pushed October 16, 2026; AGPL-3.0; independent 2026 reviews confirm the SM-2/FSRS schedulers, 100k+ card handling, free AnkiWeb sync, self-hostable sync server, and the $24.99 one-time iOS app funding model. The scheduling approach is validated by two decades of use in medical schools and language learning with published retention research behind spaced repetition generally. Strengths: the gold-standard SRS engine, enormous shared-deck library, fully free core. Docked for: (1) dated interface with a genuinely steep learning curve; (2) card creation is manual and review queues can overwhelm; (3) iOS app cost surprises users expecting free everywhere. License: AGPL-3.0 (desktop).
★ 32,059 GitHub stars
How the trust score is built
Full methodology →- Adoption · stars/downloads, log-scaled vs peers
- 10.0/10
- Maintenance · recency, releases, issue load
- 9.0/10
- Openness · license + docs
- 10.0/10
- Manual review · sanity read + red-flag check
- 8.0/10
- · ~32.1k GitHub stars (Oct 16, 2026 snapshot); AGPL-3.0 (desktop); 20+ years of development
- · SM-2 + FSRS self-optimizing scheduler; 100k+ card decks; free AnkiWeb sync + self-hostable server; thousands of shared decks; huge add-on ecosystem
- · Dated UI, steep learning curve; manual card creation; iOS app $24.99 one-time surprises users
Sources
Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.