Online learning has changed the way language learners around the world are learning Mandarin. People used to learn Chinese by memorizing and imitating. Nowadays, Chinese learners can learn it at anytime and anywhere. There are two different types of online learning: synchronous and asynchronous. For teachers and student in an asynchronous online mode, teaching and learning do not happen at the same time. And synchronous online mode, teachers and students located in different place but teaching and learning happen at the same time.
Asynchronous online mode (Vocabulary only)
There are some websites provide asynchronous online learning materials. Here are some examples: Duolingo and Memrise provide you some vocabulary flashcard for rote learning.
Anki is a free and open-source flashcard program using spaced repetition, a technique from cognitive science for fast and long-lasting memorization. Personally speaking, Anki is a better and easier choice for you to arrange your own learning material.
Synchronous online mode
Traditional classroom to online classroom
For synchronous online Chinese learning, everything is almost same as in real world, you just need to make decision to learn Chinese in a group or one-by-one. For one-by-one, who you need is someone can tutor and communicate with you. It would not be free sometimes expensive. Another option is to join a group class. The famous universities, such National Taiwan Normal University and Beijing Language and Culture University, also transform their traditional face-to-face classroom classes into online classes in COVID-19 pandemic. As you might image, no matter it is tutoring or in group, there is only one teacher in a online classroom.
Originated online classroom
Magic Ship Mandarin Online is another choice for synchronous online class to learn Chinese online, which provides two teachers in one classroom. Live interaction and feedback are important elements for learning a new language. However, the conversation is limited when the language proficiency of student is low. The traditional way is that teacher use simple, easy, childish, sometimes fake content to make learning happened. There are more possible ways of learning Chinese while two teachers in one classroom. You can join a free trial to see how this happen.
Whether synchronous and asynchronous online learning, the only thing you must invest is time. There is no short cut for learning a new language, Chinese is no exception.