# How Spaces works

Computers and Spaces, bring-your-own compute, where a Space can run, and how you and your agents reach it directly or through the relay.

> Agent discovery: use [the Cua documentation index](https://cua.ai/docs/llms.txt) to find related pages and their Markdown URLs.



Cua Spaces connects three things: the computers you own, the Spaces on them, and
the people and agents who use those Spaces.

## Computers and Spaces

A **computer** is a Mac, Windows or Linux computer
you own or rent. A **Space** is one desktop on a computer, set up for a task. A
Space is a container or a VM, or the computer's own desktop.

Cua doesn't rent computers. You bring them, and your cloud provider bills you for
any VM you run in your own account. Cua provides the app, sharing and the relay
that lets your devices reach your computers.

## Where a Space runs

| Location | What it is |
|---|---|
| This computer | A container or VM on the Mac, Windows or Linux PC you are using. |
| Another of your computers | A computer you [added](</docs/spaces/guides/add-a-computer>) that provides Spaces, such as a [spare Mac mini](</docs/spaces/guides/add-a-computer#use-a-spare-mac-to-host-spaces>). |
| Your own cloud | A VM in your own AWS, Google Cloud or Modal account. See [Choose where sandboxes run](</docs/cua-sdk/guides/local-runtimes#your-own-cloud>). |

Cua Cloud, the hosted option, has ended. See
[Cua Cloud (Fleets) has ended](</docs/cua-sdk/guides/cua-cloud-ended>).

Every Space runs `cua-spacesd`. It streams the screen, takes input through
[Cua Driver](</docs/cua-driver>), and receives teleported apps and files.

## How you reach a Space

- **Directly.** On the same network, or over Tailscale, your device connects to
  the Space with its address and a token. No account is needed, and the traffic
  doesn't use the relay.
- **Through the relay.** A computer set up with `cua host setup` joins the cua.ai
  relay with an outbound connection, so you don't open ports. Your enrolled
  devices, and people you share a Space with, reach it through the relay. Relay
  use counts toward your [plan's](</docs/spaces/guides/teams#plans>) live sessions and
  remote hours.

For what the relay can and can't see, see
[What the relay can see](</docs/spaces/guides/relay-security>).

## Space ids

| Kind | Id | Comes from |
|------|----|------------|
| Local | `local:<name>` | `spaces.create(options)`: a new Space, on this computer by default |
| Direct | `direct:<host:port>` | `spaces.add(url, token)`: an existing computer |
| Relay | `relay:<machine-id>` | Your computers set up with `cua host setup`, listed automatically |

The app, the `cua` CLI, the SDKs and `cua daemon` share one registry
(`~/.cua/spaces.json`). Relay computers come from your account's directory and
are never written to `spaces.json`.

## Who can do what

You own your computers and the Spaces on them. You can
[share a Space](</docs/spaces/guides/share-a-space>) with another account as a viewer or
an editor, and with [Teams](</docs/spaces/guides/teams>) a computer can belong to the
team instead of one person. Your agents act through the `cua` MCP server, and you
choose what each one may do. See [Connect your agent](</docs/spaces/guides/connect-your-agent>).