Gajim is a full-featured, cross-platform instant messaging client for the XMPP protocol, built with the GTK toolkit and (since the 2.x series) Python. First released in 2004, it runs on Linux, BSD, macOS, and Windows, and was described by Tom’s Hardware as the lightest and fastest jabber IM client of its era.
Key Features
End-to-end encryption — OMEMO and OpenPGP support, plus OTR via a third-party plugin.
Group chat — Full XMPP multi-user chat (MUC) support.
File transfer — Send files directly and via HTTP file upload.
Rich messaging — Emojis, avatars, read markers, and per-message hats/roles.
Multiple accounts — Manage several XMPP addresses from one interface.
Extensible — Third-party plugin system plus full service discovery (including Nodes) and an XML console for power users.
It is one of the most mature and actively developed desktop XMPP clients, balancing an easy-to-use interface with deep protocol features for advanced users. Cross-platform support makes it a solid choice for xmpp on both Linux and Windows desktops.
Use Cases
Daily secure messaging with OMEMO-encrypted conversations
Managing multiple XMPP accounts side by side
Joined group discussions with file sharing and rich formatting