An automatically generated character string is assigned as your pixiv ID when you register as a new user.
pixiv ID can be changed once for each account after registering as a new user.
Please enter a character string of your choice that consists only of 1-byte alphanumeric characters, hyphen "–" and/or underscore "_" in the entry field of pixiv ID. However, you cannot register using the same character string as an already existing pixiv ID. If string is already in use and registration is not possible then try again with a different character string.