If you're using Astro as a static site builder—its behavior out of the box—you don't need an adapter.
If you wish to [use server-side rendering (SSR)](https://docs.astro.build/en/guides/server-side-rendering/), Astro requires an adapter that matches your deployment runtime.
[Node](https://nodejs.org/en/) is a JavaScript runtime for server-side code. Frameworks like [Express](https://expressjs.com/) are built on top of it and make it easier to write server applications in Node. This adapter provides access to Node's API and creates a script to run your Astro project that can be utilized in Node applications.
## Installation
First, install the `@astrojs/node` package using your package manager. If you're using npm or aren't sure, run this in the terminal:
After [performing a build](https://docs.astro.build/en/guides/deploy/#building-your-site-locally) there will be a `dist/server/entry.mjs` module that exposes a `handler` function. This works like a [middleware](https://expressjs.com/en/guide/using-middleware.html) function: it can handle incoming requests and respond accordingly.
You can use this `handler` with any framework that supports the Node `request` and `response` objects.
For example, with Express:
```js
import express from 'express';
import { handler as ssrHandler } from './dist/server/entry.mjs';
const app = express();
app.use(ssrHandler);
app.listen(8080);
```
### Using `http`
This output script does not require you use Express and can work with even the built-in `http` and `https` node modules. The handler does follow the convention calling an error function when either
- A route is not found for the request.
- There was an error rendering.
You can use these to implement your own 404 behavior like so:
```js
import http from 'http';
import { handler as ssrHandler } from './dist/server/entry.mjs';
http.createServer(function(req, res) {
ssrHandler(req, res, err => {
if(err) {
res.writeHead(500);
res.end(err.toString());
} else {
// Serve your static assets here maybe?
// 404?
res.writeHead(404);
res.end();
}
});
}).listen(8080);
```
## Configuration
This adapter does not expose any configuration options.
