Hi @Balamurugan Mani ,
Thanks for reaching out and apologies for delay in response.
Unfortunately, as of now Azure AD B2C only supports Alphanumerical characters, and you cannot signup or sign-in with usernames containing non-alphanumeric values.
Currently username must begin with an alphabetical character or number and can only contain alphanumeric characters along the following symbols '_' and '-'.
There is similar request raised in User forum regarding non-alphanumeric characters which you can vote it for future requirement for product team.
Thanks,
Shweta
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