Language learning is popular among the user industry. There are several market players there, but the top is Duolingo. In an Aimprosoft article on language learning website development, the team mentions that the company has over 300 million users worldwide, which is almost three times higher than its main competitors.
How did they achieve such success? The key is simplicity. They allow users to learn quickly without basic knowledge of the target language. Yet, they are not the only tool needed to be used. You can achieve basic fluency on the platform, but to become good in the target language, you need to learn from additional resources.