Mir is a next generation display server targeted as a replacement for the X window server system to unlock next-generation user experiences for devices ranging from Linux desktop to mobile and IoT devices powered by Ubuntu.

If you want to use the Mir snaps, see: Run a kiosk snap on Ubuntu Core
If you want to try out the Mir demos on desktop, see: Getting and Using Mir
If you want to get involved in Mir development, see: Getting Involved in Mir

Using Mir for server development

Install the headers and libraries for using libmiral in development:

$ sudo apt install libmiral-dev

A miral.pc file is provided for use with pkg-config or other tools. For example:

$ pkg-config --cflags miral

The server API is introduced here: Introducing the Miral API

Using Mir for client development

This is usually something you don't need to do explicitly, it is normally handled by a GUI toolkit (or library).

A toolkit can run on Mir in three ways: using Wayland protocols, using the Mir client API or using X11 translation by the Xmir server.

Qt, has "wayland" and "mir" plugins that can be selected by setting the QT_QPA_PLATFORM environment variable to "wayland" or "ubuntumirclient" respectively.
SDL can be built with "wayland" and "mir" support and these options selected by setting the SDL_VIDEODRIVER environment variable to "wayland" or "mir".

If want to use the Mir client library directly (e.g. you are working on "mir" support for a toolkit or library) Install the headers and libraries for using libmirclient in development:

$ sudo apt install libmirclient-dev

A miral.pc file is provided for use with pkg-config or other tools. For example:

$ pkg-config --cflags mirclient

The client API documentation is here: MIR graphics tools API