noun
display name; screen name
Used in online services, forums, and games for the name shown to other users.
このサイトでは表示名を自由に変更できます。
On this site, you can freely change your display name.
ニックネーム is a casual nickname, while 表示名 is a more formal term used in system settings.
Compound of 表示 (display) and 名 (name). A straightforward modern term from online services.