Session capping is the practice of limiting the number of times a visitor sees an element while visiting a website.
Most often session capping is used for digital advertising by limiting the number of times an individual is exposed to a single ad during his visit of a website. For more details see ad frequency capping.
Session capping can also be used to limit the number of appearances of intrusive marketing elements for a single visitor. The goal is to limit annoyance. For instance, session capping may be used for displaying lightbox subscribe forms or proactive live chat windows.