Psi is a free GPL instant messaging client for the XMPP protocol which uses the Qt toolkit. Fast and lightweight, it runs on Linux, Microsoft Windows, Mac OS X and eComStation.
Due to Psi’s free/open-source nature, several forks have appeared, which occasionally contain features that may appear in future official Psi versions.
Because XMPP allows gateways to other services, which many servers support, it can also connect to the Yahoo! Messenger, AIM, Gadu-Gadu, ICQ and.NET Messenger Service networks. Other services available using gateway servers, include RSS and Atom news feeds, sending SMS messages to cellular networks and weather reports.
Emoticon packs are supported using the jisp format. Many jisp emoticon packs are available, including ones from AIM, iChat, and Trillian.
Psi supports file transfers between other XMPP clients, and it is possible to send or receive files from other IM networks, if the user’s servers support this. Psi supports Contact Is Typing Notification (which works with Yahoo!, MSN, and AIM contacts). Brings automatically resizing contact list and composing window in chat dialogs, tabbed chats, support for Growl messaging system on Mac OS X, window transparency and many other changes.
Thanks to the efforts of volunteers around the world, localized versions of Psi are available in almost twenty different languages. And with its built-in support for the Unicode international text standard, Psi can also send and receive messages in virtually any language. Casually converse with accents, symbols, and right-to-left text.
Psi’s appearance is highly customizable, so you can choose the colors, icons, and emoticons that suit you best
Using the same SSL technology that makes it possible for you to safely shop on the web, Psi automatically encrypts its communication with compatible IM servers to provide a secure connection over untrusted networks like public WiFi access points.