We work with many clients using Project Online and Project Server and often people want to know the differences. Project Online and Project Server 2013 on-premises are based on the same set of features and functionality, but there are differences between the two. This link provides a table with a very detailed overview of the differences between Project Online and a Project Server 2013 on-premises environment. We hope this provides you with some helpful information. For all your Project Online and Project Server needs please contact us today.