Psi is a free instant messaging application designed for the XMPP network (including Google Talk). Fast and lightweight, Psi is fully open-source and compatible with Windows, Linux, and Mac OS X.
License: Open Source
Psi is a feature-rich instant messaging client that supports multiple protocols and offers extensive customization, making it suitable for advanced users. In contrast, Instantbird is a more lightweight and user-friendly option, focusing on simplicity and speed, making it ideal for casual users.