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.

Memrise excels as a vocabulary acquisition tool, centered around a spaced repetition system (SRS) to optimize memorization. Its standout feature is the integration of thousands of short video clips of native speakers, which provides crucial exposure to authentic pronunciation and colloquialisms. In addition to official courses, Memrise hosts a vast library of user-generated content for a wide array of languages and subjects. However, it provides minimal explicit grammar instruction and limited opportunities for sentence construction or speaking practice, making it an excellent supplementary tool for vocabulary and listening rather than a comprehensive course.