Official Website: www.mudlet.org

A cross-platform, open source, and super fast MUD client with scripting in Lua.

Mudlet is a quality MUD client, designed to take mudding to a new level.

It’s a modern breed of a client on the gaming scene – with an intuitive user interface, a specially designed scripting framework, and a very fast text display. That, along with cross-platform capability and an open-source development model result in a very likable game client.
Key Features

Simple to use
Very, very fast
Active development
Big, thriving community
Powerful trigger engine
Rich Lua-based coding functionality (API)
Excellent script editor
2D and 3D mapper with autowalk
Powerful and simple to use GMCP
Discord integration
Completely themable
Open-source and Free
Cross platform: runs on Windows, macOS and Linux
Full compatibility: run same scripts on any of the above.