What does the user name usually fill in?

User names can usually consist of Chinese characters, letters, numbers or their combinations. For example, the user name can be "Everest", "zmlmf", "12345" and so on. As the identification code of the login account, the user name is unique on different websites or platforms. The choice of user name is largely limited by the naming rules of the platform. Therefore, when filling in the user name, make sure to follow the user name filling rules of the platform to avoid problems in use. The user name is the name used to log in to the network account. It is the unique identification of users on the Internet or a certain system or platform. When registering a website or using some services, users need to choose a user name that is not registered by others according to the regulations of the website. If the selected user name has been used by others, the system will generally give a prompt.