Duolingo

Duolingo's bite-sized lessons feel like games, rewarding consistency with streaks and challenges. The free tier covers most features, while Super and Max subscriptions add offline mode and personalized AI practice. The app also offers Duolingo English Test for standardized proficiency scoring.

Its strength is accessibility: you can start learning any of 40+ languages today at no cost, making it ideal for casual learners and those exploring a language before committing deeper.