Anki is a powerful, open-source flashcard program renowned for its effective spaced repetition system (SRS). It isn't a language course itself, but a highly effective tool for memorizing vocabulary, phrases, or grammar rules that you input yourself or download from shared user-created decks. Its high degree of customization allows for rich cards with audio, images, and cloze deletions. While its interface can be unintuitive for new users, its effectiveness for long-term retention is largely considered unparalleled for dedicated learners.

Busuu offers well-structured courses that balance vocabulary, grammar, and practical application. Its standout feature is the integrated community, where learners can submit writing and speaking exercises for feedback from native speakers. While the core curriculum provides a solid foundation from beginner to intermediate levels, the quality and speed of community feedback can vary. The app's speech recognition tool is functional but not its main strength, making Busuu a strong choice for those who appreciate guided learning supplemented by human interaction.