What is Urbit OS?

Urbit OS is a personal server operating system that runs on any Unix box as a self-contained virtual machine.

It's sometimes described as an "operating function": the current state of your urbit is computed by running its history through one function, called Nock. It's simple to understand, easy to secure, and trivial to reproduce exactly.

This section describes the two components of Urbit OS proper: the kernel, called "Arvo", and its standard distribution (the "%base desk") that contains other essential functionality.

If you're looking for one detailed overview of Urbit OS, read the 2016 whitepaper and this 2024 article on what's changed since the whitepaper's publication.

For information on the Urbit runtime that interprets Nock and talks to the host machine, see the runtime section.