> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/vercel/next.js/llms.txt
> Use this file to discover all available pages before exploring further.

# next start

> Start a production Next.js server after building with next build.

`next start` starts the application in production mode. The application must be compiled first with [`next build`](/api-reference/cli/next-build).

```bash theme={null}
next start [directory] [options]
```

## Options

<ParamField path="[directory]" type="string">
  The directory containing the Next.js application. Defaults to the current working directory.
</ParamField>

<ParamField path="-p / --port <port>" type="number" default="3000">
  Port number to listen on. Can also be set via the `PORT` environment variable.
</ParamField>

<ParamField path="-H / --hostname <hostname>" type="string" default="0.0.0.0">
  Hostname to bind the server to.
</ParamField>

<ParamField path="--keepAliveTimeout <milliseconds>" type="number">
  Maximum time in milliseconds to wait before closing inactive keep-alive connections. Important when deploying behind a load balancer.
</ParamField>

<ParamField path="--experimental-cpu-prof" type="boolean">
  Enable CPU profiling via V8's inspector. Profiles are saved to `.next/cpu-profiles/` on process exit.
</ParamField>

<ParamField path="-h / --help" type="boolean">
  Show all available options.
</ParamField>

## Environment variables at start time

Environment variables loaded by `next start` depend on where they are defined:

| Source             | When loaded | Notes                                    |
| ------------------ | ----------- | ---------------------------------------- |
| `.env`             | Build time  | Values baked into the bundle             |
| `.env.local`       | Build time  | Local overrides, not committed           |
| `.env.production`  | Build time  | Production-only values                   |
| System environment | Runtime     | Set in your deployment platform or shell |

`NEXT_PUBLIC_*` variables are inlined at build time and cannot be changed at start time. Server-only variables (without the `NEXT_PUBLIC_` prefix) can be changed between builds if you read them at request time.

<Note>
  `PORT` cannot be set in `.env` files. The HTTP server starts before environment files are loaded. Pass `PORT` as a system environment variable or use the `-p` flag.
</Note>

## Examples

### Start on a custom port

```bash theme={null}
next start -p 8080
# or
PORT=8080 next start
```

### Bind to a specific hostname

```bash theme={null}
next start --hostname 127.0.0.1
```

### Configure keep-alive timeout for a load balancer

When deploying behind a load balancer (e.g. AWS ELB/ALB), set the keep-alive timeout to a value greater than the load balancer's idle timeout to prevent connection termination errors:

```bash theme={null}
next start --keepAliveTimeout 70000
```

### CPU profiling

```bash theme={null}
next start --experimental-cpu-prof
```

Profiles are saved as `start-main-*.cpuprofile` in `.next/cpu-profiles/`. Open them in Chrome DevTools under the Performance tab.

### Serving a standalone build

If you built with `output: 'standalone'`, use the generated minimal server instead of `next start`:

```bash theme={null}
# Copy static assets first
cp -r public .next/standalone/ && cp -r .next/static .next/standalone/.next/

# Start the standalone server
node .next/standalone/server.js
```

The standalone server reads `PORT` and `HOSTNAME` environment variables:

```bash theme={null}
PORT=8080 HOSTNAME=0.0.0.0 node .next/standalone/server.js
```

## Version history

| Version   | Changes                                            |
| --------- | -------------------------------------------------- |
| `v15.0.0` | Turbopack stable for `dev`; `next start` unchanged |
| `v13.0.0` | App Router support added                           |