Built upon an open protocol named Jabber, Psi is a fast and lightweight messaging client that utilises the best in open source technologies. The goal of the Psi project is to create a powerful, yet easy-to-use Jabber/XMPP client that tries to strictly adhere to the XMPP drafts and Jabber JEPs. This means that in most cases, Psi will not implement a feature unless there is an accepted standard for it in the Jabber community. Doing so ensures that Psi will be compatible, stable, and predictable, both from an end-user and developer standpoint.

Unlike other IM clients, Psi is small, fast and responsive. It uses a graphical toolkit called Qt, which takes on the appearance of whichever operating system you run it on. For this reason, Psi doesn't use 'skins'.

Psi has full support for Unicode. Unicode allows Psi to send and receive messages in other languages, even ones that aren't based upon the English letterset. In fact, you are able to use Psi in your choice of eight different languages, with more on the way!