Mocksup allows for two kinds of projects: public and private.
Public projects
Public projects are unlimited — meaning even a Mocksup user on a free account can create as many of them as they want — and viewable by anyone.
Public projects are great for garnering feedback on a project from the web as a whole.
You can view some real life examples of public projects at our Examples page.
Private projects
In order for someone to view and provide feedback on a private project, they have to be explicitly invited by an admin or project collaborator. Otherwise they get an error message saying they don't have access to that project.
Free accounts can create one private project, but after that the number of private projects you can create is limited by the plan you have.