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.

Readlang helps you learn a language by reading authentic content from across the web. As a browser extension and web app, it allows you to click on any word or phrase you don’t know on a webpage to get an instant translation. These translated words are automatically saved as flashcards for later review via spaced repetition. It is an exceptional tool for intermediate-to-advanced learners looking to transition to native materials and expand their vocabulary contextually, but it is primarily a reading and vocabulary tool with no speaking component.