PSI is one of the world's most popular Jabber clients running on Windows, Linux and Mac OS X. The most important features of the application include support for several accounts at the same time, built-in browser of Jabber services (possibility to add support for SMS, more networks including Gadu-Gadu, Google Talk, Tlen... The system can be used to encrypt conversations with OpenPGP keys and connections with OpenSSL keys (SSL/TSL), file transfer function, assigning avatars to contacts, autoresponder or built-in XML console.

Although the communicator does not look very attractive after the first start-up, it makes up for the functionality and simplicity of use.