noun
main account; primary account
Refers to one's primary account on social media, online services, or games, as opposed to a sub-account or alt account.
メインアカウントでログインしてください。
Please log in with your main account.
サブ垢よりメインアカウントのほうがフォロワーが多い。
My main account has more followers than my sub-account.