username

A username is a unique identifier assigned to a user within a computer system, service, or network that is used to authenticate the user and differentiate them from others. It is typically chosen by the user or assigned by an administrator and is used, together with a password or other factors, to verify identity during sign-in. A username is not the same as a display name; the latter is how a person is shown to other users and may be changeable, while the username is usually fixed and used for logins and records.

In practice, usernames are required to be unique within a given system and must conform to length and character restrictions. Common conventions include letters, numbers, and underscores; some systems are case-sensitive, others are not. Some services allow email addresses to serve as usernames, while others require a separate handle or alias.

Security and privacy considerations include avoiding the use of personally identifiable information, as well as not reusing usernames across different sites to limit identity exposure. Users may prefer combining a stable identifier with a random element to reduce guessing, and administrators often enforce policies to prevent impersonation and offensive terms.

Creation tips: check system rules, avoid real names if privacy matters, consider future scaling, and ensure the username is easy to remember but not easily guessable. In many environments, the username is connected to the account in logs, permissions, and access controls, making its consistency important for auditing and support.