> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nanoforge.eu/llms.txt
> Use this file to discover all available pages before exploring further.

# Environment variables

> Pass configuration to the client and server at runtime

import { Note } from "mintlify/components";

## Overview

When running a NanoForge game (via `nf start`), environment variables can be passed to the client
and server through a `.env` file at the root of the project, or directly from the environment.

```dotenv theme={null}
NANOFORGE_CLIENT_SERVER_TCP_PORT=4445
NANOFORGE_CLIENT_SERVER_UDP_PORT=4444
NANOFORGE_CLIENT_SERVER_ADDRESS=127.0.0.1
```

## Scoping by prefix

Variables are scoped by their prefix, which controls where they are available:

| Prefix              | Availability                        |
| ------------------- | ----------------------------------- |
| `NANOFORGE_CLIENT_` | Available in the client only        |
| `NANOFORGE_SERVER_` | Available in the server only        |
| `NANOFORGE_`        | Available in both client and server |

<Note>
  Prefixes are stripped before the variable is exposed to libraries. For example,
  `NANOFORGE_CLIENT_SERVER_ADDRESS` is exposed to the client as `SERVER_ADDRESS`.
</Note>

For full documentation on how libraries consume these variables, see
[`@nanoforge-dev/config`](https://github.com/NanoForge-dev/Engine/tree/main/packages/config).