I have noticed that a lot of websites only allow a fixed amount of username changes, and does not allow the reuse of a previously or currently used username. For example, on Fandom.com once a username is used, it can never be used again. On Twitter.com, usernames cannot be less than 6 characters. On Reddit and Gmail, usernames can never be changed or reused, not even once.

As such, there is not a lot of freedom with usernames. It seems like all of the desirable ones are taken, or were taken, or you cannot change your username, or the requested username does not fall under the length requirements.

Is it possible for Usernames to be, at the same time,

  1. Able to be changed an unlimited number of times
  2. Able to be reused
  3. Able to be any length desirable, to a maximum of 2000 bytes
  4. Able to include any characters in Unicode

Since no platform I know of has these qualities in their setup of usernames, is it even possible to have a username layout that has the above 4 qualities?

  • 2
    Anything is possible. Why is it relevant to security?
    – Chenmunka
    Jun 13, 2023 at 17:58
  • You can program a system to accept whatever username structure you'd like ...
    – schroeder
    Jun 13, 2023 at 19:15
  • As I said, you can program a system to accept whatever username structure you'd like ...
    – schroeder
    Jun 13, 2023 at 20:52
  • This is looking less and less like a security question.
    – schroeder
    Jun 13, 2023 at 20:53
  • Take this site for example. It accepts 3-character usernames, and there are many "god" users. Max limits of usernames and what character strings are accepted are things usually determined by the database that's used,
    – schroeder
    Jun 13, 2023 at 20:56

1 Answer 1


It depends on what exactly the purpose of the username is. If it's just information that should be displayed, then the username can have any property you want. However, if it's used during the log-in procedure, then it probably should be unique, because you don't want people to guess which account is theirs. And if the name is used to uniquely identify users (either within the system or between users), then it should be unique and relatively simple (Unicode can be abused for similar-looking characters) and somewhat stable. That's why websites choose to impose specific restrictions.

  • The restrictions are the consequence of specific requirements. Website owners (hopefully) have a clear idea what the usernames should be used for and which properties they should have. Then they'll choose appropriate rules. There's no universal rule that forbids 2000-character long usernames from the entire Unicode set.
    – Ja1024
    Jun 13, 2023 at 18:25

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