What Urbit is
Urbit is a virtual city of general-purpose personal servers.
Your old personal server
What's a personal server? In a sense, you already have one. Your personal server is the combination of all the cloud services you use now.
This "server" is a mess. It's broken into 17 different fragments which are scattered all over the planet. You have no control at all over any of the pieces. The more we depend on Web services, the more we realize how unsustainable this situation is.
Can you remember all the services you have accounts for? How about the username and password for each? Some of them will let you pull your data out somehow, some won't. Sometimes you can move your data between them, sometimes you can't. But they're all good at showing you ads.
Your new personal server
Your urbit is your own general-purpose server. It holds your data; runs your apps; wrangles your connected devices; and defines your secure identity. If you still need your old services, it drives them with APIs.
Your urbit presents your whole digital life as a single web service. And since it's yours, open source and patent-free, it never shows you ads. Or loses your data. Or updates without your consent.
Technically, Urbit is a new kind of OS that has a precise formal definition. (Urbit is actually a single mathematical function.) One advantage of a math-based OS is that Urbit is perfectly portable. It can't tell whether it's in a cloud data center or on your home PC.
Concerned about mass surveillance? Download your urbit and restart it on your laptop, or move to a new host in Iceland. Urbit's formal simplicity makes managing it as easy as managing an iPhone: all you have to decide is what apps to add.
Each urbit is a node on a global, encrypted P2P network. Your Urbit name, a generated pseudonym like
~talsur-todres, is also your network address. Like Bitcoin, Urbit address space is a cryptographic asset with a limited supply.
By keeping addresses scarce, we make spam and abuse expensive. Urbit is a "friendly network," like the Internet in 1986, where a stranger is nice until proven nasty. As it matures, Urbit will grow into a decentralized, self-governing virtual city both safe and free.
The Urbit future
In an Urbit world, your data is no longer trapped in a jumble of proprietary servers. Your urbit is a permanent, versioned, typed archive the size of your digital life. Even before you move your data from a Web service to a local Urbit app, your urbit can drive your account with an API or scraper.
And within Urbit, data is never locked inside apps. Imagine if you could painlessly switch between Facebook and Google+, Asana and Trello, Tumblr and WordPress. Not only does your urbit upgrade itself and its apps automatically, you can "sidegrade" a running app to another vendor without losing data.
Your urbit is also your digital identity. Along with your data lifestream of media, messages and documents, it has the keys and tokens to manage all your legacy Web services. It holds the keys for your cryptocurrency wallets, so it can buy and sell for you. (With one personal server to secure, not 17 different accounts, you actually have the bandwidth to take security seriously.)
You still use network services. But instead of interacting with the service provider's HTML UI, which phones home using proprietary HTTP APIs, you interact with a third-party app on your urbit, which talks to multiple service providers using public, typed Urbit protocols. For example, your urbit runs a single shopping app, which downloads catalogs and uploads orders. This app is one store which sells everything in the world, with a salesman who's 100% on your side and always has the best price. Every computing experience is different when the UI is working exclusively for the user.
Finally, your urbit is the hub for your network of connected devices. Your smart thermostat, your wristband, your phone and tablet, all run satellite urbits which talk securely to your main urbit in the cloud.
A chance for digital freedom
The promise of the personal server isn't just convenience. General-purpose computing is magic. This magic must be in the hands of all, not just those who can master Unix. The computer is a bicycle for the mind. It's an open vehicle for exploration and discovery. It's not a way to optimize ad delivery.
Urbit, as virtual city, is a platform that brings together all our datastreams -- from emails to heartbeats -- in a way that we ourselves control. Can we work together to match faces in photos, without submitting to some panopticon in Mountain View? While the first step in freedom is the right to be left alone, the second is the power to form new intentional communities, to create and evolve a voluntary definition of public space. We have no idea at all what people will do with this power.
General-purpose computing is digital freedom. And today, a cloud data center is the technically optimal locus of computation. The cloud is always on, always available, never loses data. Hosts are sometimes attacked; but they never intentionally tamper with their virtual computers. The cloud can never be secure against a global adversary; but most people don't have a global adversary. A single portable platform provides "herd immunity" for the few who do need direct physical control over their main computers.
Though even laptops are atrophying into mere browsers, mass-market, general-purpose computing on the client side remains an endangered species that must be protected. But on the server side, this species has never even existed. There has never been anything like a mass-market personal server. Why not?
Freedom is an engineering problem
Urbit is not a difficult idea. Urbit is like a flying car: the idea is not the hard part. Almost everyone we talk to about Urbit turns out to have had pretty much the same idea themselves. The problem is building it.
A server is a computer. It's running some operating system. This OS is a flavor of Unix. There are no alternatives. It's connected to some network. This network is the Internet. It has no competitors. You can have a personal server, if it's a Unix server on the Internet.
Almost no one thinks being a Unix system administrator is fun. Not even Unix system administrators think running an Internet server is fun. So the personal Unix/Internet server is like the personal bulldozer. This is not a consumer product. Any number of engineers can't turn a bulldozer into a bicycle.
How did we build the personal bulldozer? We didn't. We started from scratch. (The people who built the first PCs didn't start with a mainframe OS, either.) We created a new platform: Urbit.
Urbit doesn't compete with Unix and the Internet. It's a new, opaque layer on top of them. Your browser runs on a native OS, but it doesn't give Web apps any way to talk to the native OS. Urbit is like a browser for the server side: code within Urbit is formally isolated from the platform it runs on top of.
Your urbit is a Unix process, in a data center or your PC. It sends UDP packets over the Internet. It can both load and serve web pages over HTTP. Except for character sets and crypto, nothing in Urbit reuses or depends on any 20th-century code.
Urbit is a complete, clean-slate system software stack: a non-lambda interpreter (Nock), a functional language (Hoon), and an event-driven OS (Arvo), with its own encrypted protocol (Ames), typed revision control (Clay), reactive web server (Eyre) and functional build system (Ford). The full system, including basic apps, is only 30,000 lines of Hoon.
The first end-to-end prototype of Urbit took one engineer eleven years. The current beta took three more years, with about three engineers on average.
How does it take 14 years to write 30,000 lines of code? The code wasn't the hard part. The hard part was rewriting it until it was right. We think we've solved all the real CS problems, and we're certainly done changing major interfaces. But it will take more than our small team to deliver a polished Urbit user experience that can actually challenge modern web apps.
Where we are, what we're doing
Urbit is in feature freeze. It's a minimum viable product in early beta. It still needs quite a bit of fit-and-finish work. We certainly don't recommend it for end users or consider it in any way secure. But it's fun to play with, if you're a hacker.
This summer, we're making the switch to an open and transparent development and specification process. A system as unusual as Urbit can't be invented in public. But it has to be finished and maintained in public.
Additionally, we're creating an open political and economic process, with a small, fixed-price public presale of Urbit address space. Join us and help make this future actually happen.
To keep reading, learn more about Urbit's address space; share our vision of the Urbit user experience, from the top down or the bottom up; check out the development roadmap; evaluate Urbit's beliefs and principles or its interim constitution.
(For technical readers, check out our documentation or the whitepaper).