DuoNinja is a vocabulary learning tool that helps users practice words in a way their memory actually keeps. It uses spaced repetition, real example sentences, and audio to make vocabulary stick through daily streaks and consistent practice.

The product includes example sentences and audio for each flashcard so you can see how words are really used. It features spaced repetition that shows cards when you're about to forget them, helping words stick with less effort. Users can build their own decks or copy community decks to start studying right away.

DuoNinja gives users full control over their learning experience. You can customize language variants, choose from hundreds of high-quality voices for example sentences, and tune the SRS algorithm to match your learning pace. The system allows you to pick specific locales like Brazilian Portuguese or Mexican Spanish.

The main benefit is making vocabulary retention more effective through scientifically-backed spaced repetition. It helps users build consistent learning habits with daily streaks and provides contextual learning through real example sentences and audio pronunciations.

The product targets Duolingo users who want to reinforce their vocabulary learning. It integrates with Duolingo through a browser extension that imports vocabulary directly from the language learning platform.