samidori is a free online Japanese course from the University of Kyoto, and as you might expect, it’s a comprehensive, well-organized introduction to the language.
There is an extensive range of lessons from absolute beginner up to lower intermediate. They cover the kana, grammar, vocabulary, listening, and reading. However, there are no writing or speaking activities, and although you’ll learn to recognize them, you won’t be taught how to write any kanji. Higher levels also contain fewer lessons than the lower levels.
Most of the lessons follow the same format: the lesson topic and vocabulary are introduced in both Japanese and English, then there are example sentences, audio recordings for the vocabulary and example sentences, and finally practice questions.
For beginners, samidori is a decent introduction to Japanese, although you’ll want to pair it with kanji studies and writing and speaking practice. Intermediate learners, however, will likely want to use it as a supplementary resource only.