# Static site generation

To use SvelteKit as a static site generator (SSG), use [`adapter-static`](https://github.com/sveltejs/kit/tree/main/packages/adapter-static).

This will prerender your entire site as a collection of static files. If you'd like to prerender only some pages and dynamically server-render others, you will need to use a different adapter together with [the `prerender` option](page-options#prerender).

## Usage

Install with `npm i -D @sveltejs/adapter-static`, then add the adapter to your `svelte.config.js`:

```js
/// file: svelte.config.js
import adapter from '@sveltejs/adapter-static';

/** @type {import('@sveltejs/kit').Config} */
const config = {
	kit: {
		adapter: adapter({
			// default options are shown. On some platforms
			// these options are set automatically — see below
			pages: 'build',
			assets: 'build',
			fallback: undefined,
			precompress: false,
			strict: true
		})
	}
};

export default config;
```

...and add the [`prerender`](page-options#prerender) option to your root layout:

```js
/// file: src/routes/+layout.js
// If you're using a fallback (i.e. SPA mode) you don't need to prerender all
// pages by setting this here, but should prerender as many as possible to
// avoid large performance and SEO impacts
export const prerender = true;
```

> [!NOTE] You must ensure SvelteKit's [`trailingSlash`](page-options#trailingSlash) option is set appropriately for your environment. If your host does not render `/a.html` upon receiving a request for `/a` then you will need to set `trailingSlash: 'always'` in your root layout to create `/a/index.html` instead.

## Zero-config support

Some platforms have zero-config support (more to come in future):

- [Vercel](https://vercel.com)

On these platforms, you should omit the adapter options so that `adapter-static` can provide the optimal configuration:

```js
/// file: svelte.config.js
import adapter from '@sveltejs/adapter-static';

/** @type {import('@sveltejs/kit').Config} */
const config = {
	kit: {
		adapter: adapter(---{...}---)
	}
};

export default config;
```

## Options

### pages

The directory to write prerendered pages to. It defaults to `build`.

### assets

The directory to write static assets (the contents of `static`, plus client-side JS and CSS generated by SvelteKit) to. Ordinarily this should be the same as `pages`, and it will default to whatever the value of `pages` is, but in rare circumstances you might need to output pages and assets to separate locations.

### fallback

To create a [single page app (SPA)](single-page-apps) you must specify the name of the fallback page to be generated by SvelteKit, which is used as the entry point for URLs that have not been prerendered. This is commonly `200.html`, but can vary depending on your deployment platform. You should avoid `index.html` where possible to avoid conflicting with a prerendered homepage. 

> This option has large negative performance and SEO impacts. It is only recommended in certain circumstances such as wrapping the site in a mobile app. See the [single page apps](single-page-apps) documentation for more details and alternatives.

### precompress

If `true`, precompresses files with brotli and gzip. This will generate `.br` and `.gz` files.

### strict

By default, `adapter-static` checks that either all pages and endpoints (if any) of your app were prerendered, or you have the `fallback` option set. This check exists to prevent you from accidentally publishing an app where some parts of it are not accessible, because they are not contained in the final output. If you know this is ok (for example when a certain page only exists conditionally), you can set `strict` to `false` to turn off this check.

## GitHub Pages

When building for [GitHub Pages](https://docs.github.com/en/pages/getting-started-with-github-pages/about-github-pages), if your repo name is not equivalent to `your-username.github.io`, make sure to update [`config.kit.paths.base`](configuration#paths) to match your repo name. This is because the site will be served from `https://your-username.github.io/your-repo-name` rather than from the root.

You'll also want to generate a fallback `404.html` page to replace the default 404 page shown by GitHub Pages.

A config for GitHub Pages might look like the following:

```js
// @errors: 2322
/// file: svelte.config.js
import adapter from '@sveltejs/adapter-static';

/** @type {import('@sveltejs/kit').Config} */
const config = {
	kit: {
		adapter: adapter({
			fallback: '404.html'
		}),
		paths: {
			base: process.argv.includes('dev') ? '' : process.env.BASE_PATH
		}
	}
};

export default config;
```

You can use GitHub actions to automatically deploy your site to GitHub Pages when you make a change. Here's an example workflow:

```yaml
### file: .github/workflows/deploy.yml
name: Deploy to GitHub Pages

on:
  push:
    branches: 'main'

jobs:
  build_site:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      # If you're using pnpm, add this step then change the commands and cache key below to use `pnpm`
      # - name: Install pnpm
      #   uses: pnpm/action-setup@v3
      #   with:
      #     version: 8

      - name: Install Node.js
        uses: actions/setup-node@v4
        with:
          node-version: 20
          cache: npm

      - name: Install dependencies
        run: npm i

      - name: build
        env:
          BASE_PATH: '/${{ github.event.repository.name }}'
        run: |
          npm run build

      - name: Upload Artifacts
        uses: actions/upload-pages-artifact@v3
        with:
          # this should match the `pages` option in your adapter-static options
          path: 'build/'

  deploy:
    needs: build_site
    runs-on: ubuntu-latest

    permissions:
      pages: write
      id-token: write

    environment:
      name: github-pages
      url: ${{ steps.deployment.outputs.page_url }}

    steps:
      - name: Deploy
        id: deployment
        uses: actions/deploy-pages@v4
```

If you're not using GitHub actions to deploy your site (for example, you're pushing the built site to its own repo), add an empty `.nojekyll` file in your `static` directory to prevent Jekyll from interfering.