Also called a ghost ban, or stealth ban, a shadow ban is a method of banning a user from a service without notifying them. When a user is shadow banned from a social network or forum, the service may appear to work normally for that person. However, their content is hidden from other users. The user's posts are not promoted on the service the same way other posts are.
A shadow ban helps prohibit users from misusing a platform, as there is less possibility for the user to dispute the ban. It also helps prevent users from attempting to use other methods to access a specific website or application.