Configuration Reference

The following reference covers all supported configuration options in Astro. To learn more about configuring Astro, read our guide on Configuring Astro.

import { defineConfig } from 'astro/config'

export default defineConfig({
  // your configuration options here...
})

Type: string
CLI: --root
Default: "." (current working directory)

You should only provide this option if you run the astro CLI commands in a directory other than the project root directory. Usually, this option is provided via the CLI instead of the Astro config file, since Astro needs to know your project root before it can locate your config file.

If you provide a relative path (ex: --root: './my-project') Astro will resolve it against your current working directory.

{
  root: './my-project-directory'
}

$ astro build --root ./my-project-directory

Type: string
Default: "./src"

Set the directory that Astro will read your site from.

The value can be either an absolute file system path or a path relative to the project root.

{
  srcDir: './www'
}

Type: string
Default: "./public"

Set the directory for your static assets. Files in this directory are served at / during dev and copied to your build directory during build. These files are always served or copied as-is, without transform or bundling.

The value can be either an absolute file system path or a path relative to the project root.

{
  publicDir: './my-custom-publicDir-directory'
}

Type: string
Default: "./dist"

Set the directory that astro build writes your final build to.

The value can be either an absolute file system path or a path relative to the project root.

{
  outDir: './my-custom-build-directory'
}

See Also:

• build.server

Type: string
Default: "./node_modules/.astro"

Set the directory for caching build artifacts. Files in this directory will be used in subsequent builds to speed up the build time.

The value can be either an absolute file system path or a path relative to the project root.

{
  cacheDir: './my-custom-cache-directory'
}

Type: Record.<string, RedirectConfig>
Default: {}

Specify a mapping of redirects where the key is the route to match and the value is the path to redirect to.

You can redirect both static and dynamic routes, but only to the same kind of route. For example you cannot have a '/article': '/blog/[...slug]' redirect.

{
  redirects: {
    '/old': '/new',
    '/blog/[...slug]': '/articles/[...slug]',
  }
}

For statically-generated sites with no adapter installed, this will produce a client redirect using a <meta http-equiv="refresh"> tag and does not support status codes.

When using SSR or with a static adapter in output: static mode, status codes are supported. Astro will serve redirected GET requests with a status of 301 and use a status of 308 for any other request method.

You can customize the redirection status code using an object in the redirect config:

{
  redirects: {
    '/other': {
      status: 302,
      destination: '/place',
    },
  }
}

Type: string

Your final, deployed URL. Astro uses this full URL to generate your sitemap and canonical URLs in your final build. It is strongly recommended that you set this configuration to get the most out of Astro.

{
  site: 'https://www.my-site.dev'
}

Type: boolean
Default: false

This is an option to minify your HTML output and reduce the size of your HTML files. When enabled, Astro removes all whitespace from your HTML, including line breaks, from .astro components. This occurs both in development mode and in the final build. To enable this, set the compressHTML flag to true.

{
  compressHTML: true
}

Type: string

The base path to deploy to. Astro will use this path as the root for your pages and assets both in development and in production build.

In the example below, astro dev will start your server at /docs.

{
  base: '/docs'
}

When using this option, all of your static asset imports and URLs should add the base as a prefix. You can access this value via import.meta.env.BASE_URL.

By default, the value of import.meta.env.BASE_URL includes a trailing slash. If you have the trailingSlash option set to 'never', you will need to add it manually in your static asset imports and URLs.

<a href="/docs/about/">About</a>
<img src=`${import.meta.env.BASE_URL}image.png`>

Type: 'always' | 'never' | 'ignore'
Default: 'ignore'

Set the route matching behavior of the dev server. Choose from the following options:

• 'always' - Only match URLs that include a trailing slash (ex: “/foo/“)
• 'never' - Never match URLs that include a trailing slash (ex: “/foo”)
• 'ignore' - Match URLs regardless of whether a trailing ”/” exists

Use this configuration option if your production host has strict handling of how trailing slashes work or do not work.

You can also set this if you prefer to be more strict yourself, so that URLs with or without trailing slashes won’t work during development.

{
  // Example: Require a trailing slash during development
  trailingSlash: 'always'
}

See Also:

• build.format

Type: 'where' | 'class'
Default: 'where'

Specify the strategy used for scoping styles within Astro components. Choose from:

• 'where' - Use :where selectors, causing no specifity increase.
• 'class' - Use class-based selectors, causing a +1 specifity increase.

Using 'class' is helpful when you want to ensure that element selectors within an Astro component override global style defaults (e.g. from a global stylesheet). Using 'where' gives you more control over specifity, but requires that you use higher-specifity selectors, layers, and other tools to control which selectors are applied.

Type: AstroIntegration

Deploy to your favorite server, serverless, or edge host with build adapters. Import one of our first-party adapters for Netlify, Vercel, and more to engage Astro SSR.

See our Server-side Rendering guide for more on SSR, and our deployment guides for a complete list of hosts.

import netlify from '@astrojs/netlify/functions';
{
  // Example: Build for Netlify serverless deployment
   adapter: netlify(),
}

See Also:

• output

Type: 'static' | 'server' | 'hybrid'
Default: 'static'

Specifies the output target for builds.

• ‘static’ - Building a static site to be deploy to any static host.
• ‘server’ - Building an app to be deployed to a host supporting SSR (server-side rendering).
• ‘hybrid’ - Building a static site with a few server-side rendered pages.

import { defineConfig } from 'astro/config';

export default defineConfig({
  output: 'static'
})

See Also:

• adapter

Type: ('file' | 'directory')
Default: 'directory'

Control the output file format of each page.

• If ‘file’, Astro will generate an HTML file (ex: “/foo.html”) for each page.
• If ‘directory’, Astro will generate a directory with a nested index.html file (ex: “/foo/index.html”) for each page.

{
  build: {
    // Example: Generate `page.html` instead of `page/index.html` during build.
    format: 'file'
  }
}

Setting build.format controls what Astro.url is set to during the build. When it is:

• directory - The Astro.url.pathname will include a trailing slash to mimic folder behavior; ie /foo/.
• file - The Astro.url.pathname will include .html; ie /foo.html.

This means that when you create relative URLs using new URL('./relative', Astro.url), you will get consistent behavior between dev and build.

To prevent inconsistencies with trailing slash behaviour in dev, you can restrict the trailingSlash option to 'always' or 'never' depending on your build format:

• directory - Set trailingSlash: 'always'
• file - Set trailingSlash: 'never'

Type: string
Default: './dist/client'

Controls the output directory of your client-side CSS and JavaScript when output: 'server' or output: 'hybrid' only. outDir controls where the code is built to.

This value is relative to the outDir.

{
  output: 'server', // or 'hybrid'
  build: {
    client: './client'
  }
}

Type: string
Default: './dist/server'

Controls the output directory of server JavaScript when building to SSR.

This value is relative to the outDir.

{
  build: {
    server: './server'
  }
}

Type: string
Default: '_astro'

Specifies the directory in the build output where Astro-generated assets (bundled JS and CSS for example) should live.

{
  build: {
    assets: '_custom'
  }
}

See Also:

• outDir

Type: string
Default: undefined

Specifies the prefix for Astro-generated asset links. This can be used if assets are served from a different domain than the current site.

For example, if this is set to https://cdn.example.com, assets will be fetched from https://cdn.example.com/_astro/... (regardless of the base option). You would need to upload the files in ./dist/_astro/ to https://cdn.example.com/_astro/ to serve the assets. The process varies depending on how the third-party domain is hosted. To rename the _astro path, specify a new directory in build.assets.

{
  build: {
    assetsPrefix: 'https://cdn.example.com'
  }
}

Type: string
Default: 'entry.mjs'

Specifies the file name of the server entrypoint when building to SSR. This entrypoint is usually dependent on which host you are deploying to and will be set by your adapter for you.

Note that it is recommended that this file ends with .mjs so that the runtime detects that the file is a JavaScript module.

{
  build: {
    serverEntry: 'main.mjs'
  }
}

Type: boolean
Default: true

Specifies whether redirects will be output to HTML during the build. This option only applies to output: 'static' mode; in SSR redirects are treated the same as all responses.

This option is mostly meant to be used by adapters that have special configuration files for redirects and do not need/want HTML based redirects.

{
  build: {
    redirects: false
  }
}

Type: 'always' | 'auto' | 'never'
Default: never

Control whether project styles are sent to the browser in a separate css file or inlined into <style> tags. Choose from the following options:

• 'always' - project styles are inlined into <style> tags
• 'auto' - only stylesheets smaller than ViteConfig.build.assetsInlineLimit (default: 4kb) are inlined. Otherwise, project styles are sent in external stylesheets.
• 'never' - project styles are sent in external stylesheets

{
  build: {
    inlineStylesheets: `auto`,
  },
}

Type: boolean
Default: false

Defines how the SSR code should be bundled when built.

When split is true, Astro will emit a file for each page. Each file emitted will render only one page. The pages will be emitted inside a dist/pages/ directory, and the emitted files will keep the same file paths of the src/pages directory.

{
  build: {
    split: true
  }
}

Type: boolean
Default: false

Defines whether or not any SSR middleware code will be bundled when built.

When enabled, middleware code is not bundled and imported by all pages during the build. To instead execute and import middleware code manually, set build.excludeMiddleware: true:

{
  build: {
    excludeMiddleware: true
  }
}

Customize the Astro dev server, used by both astro dev and astro preview.

{
  server: { port: 1234, host: true}
}

To set different configuration based on the command run (“dev”, “preview”) a function can also be passed to this configuration option.

{
  // Example: Use the function syntax to customize based on command
  server: ({ command }) => ({ port: command === 'dev' ? 3000 : 4000 })
}

Type: string | boolean
Default: false

Set which network IP addresses the server should listen on (i.e. non-localhost IPs).

• false - do not expose on a network IP address
• true - listen on all addresses, including LAN and public addresses
• [custom-address] - expose on a network IP address at [custom-address] (ex: 192.168.0.1)

Type: number
Default: 3000

Set which port the server should listen on.

If the given port is already in use, Astro will automatically try the next available port.

{
  server: { port: 8080 }
}

Type: OutgoingHttpHeaders
Default: {}

Set custom HTTP response headers to be sent in astro dev and astro preview.

Type: Object
Default: {entrypoint: 'astro/assets/services/squoosh', config?: {}}

Set which image service is used for Astro’s experimental assets support.

The value should be an object with an entrypoint for the image service to use and optionally, a config object to pass to the service.

The service entrypoint can be either one of the included services, or a third-party package.

{
  image: {
    // Example: Enable the Sharp-based image service
    service: { entrypoint: 'astro/assets/services/sharp' },
  },
}

Type: Array.<string>
Default: {domains: []}

Defines a list of permitted image source domains for local image optimization. No other remote images will be optimized by Astro.

This option requires an array of individual domain names as strings. Wildcards are not permitted. Instead, use image.remotePatterns to define a list of allowed source URL patterns.

{
  image: {
    // Example: Allow remote image optimization from a single domain
    domains: ['astro.build'],
  },
}

Type: Array.<RemotePattern>
Default: {remotePatterns: []}

Defines a list of permitted image source URL patterns for local image optimization.

remotePatterns can be configured with four properties:

1. protocol
2. hostname
3. port
4. pathname

{
  image: {
    // Example: allow processing all images from your aws s3 bucket
    remotePatterns: [{
      protocol: 'https',
      hostname: '**.amazonaws.com',
    }],
  },
}

You can use wildcards to define the permitted hostname and pathname values as described below. Otherwise, only the exact values provided will be configured: hostname:

• Start with ’**.’ to allow all subdomains (‘endsWith’).
• Start with ’*.’ to allow only one level of subdomain.

pathname:

• End with ’/**’ to allow all sub-routes (‘startsWith’).
• End with ’/*’ to allow only one level of sub-route.

Type: boolean
Default: false

Control whether Markdown draft pages should be included in the build.

A Markdown page is considered a draft if it includes draft: true in its frontmatter. Draft pages are always included & visible during development (astro dev) but by default they will not be included in your final build.

{
  markdown: {
    // Example: Include all drafts in your final build
    drafts: true,
  }
}

Type: Partial<ShikiConfig>

Shiki configuration options. See the Markdown configuration docs for usage.

Type: 'shiki' | 'prism' | false
Default: shiki

Which syntax highlighter to use, if any.

• shiki - use the Shiki highlighter
• prism - use the Prism highlighter
• false - do not apply syntax highlighting.

{
  markdown: {
    // Example: Switch to use prism for syntax highlighting in Markdown
    syntaxHighlight: 'prism',
  }
}

Type: RemarkPlugins

Pass remark plugins to customize how your Markdown is built. You can import and apply the plugin function (recommended), or pass the plugin name as a string.

import remarkToc from 'remark-toc';
{
  markdown: {
    remarkPlugins: [remarkToc]
  }
}

Type: RehypePlugins

Pass rehype plugins to customize how your Markdown’s output HTML is processed. You can import and apply the plugin function (recommended), or pass the plugin name as a string.

import rehypeMinifyHtml from 'rehype-minify';
{
  markdown: {
    rehypePlugins: [rehypeMinifyHtml]
  }
}

Type: boolean
Default: true

Astro uses GitHub-flavored Markdown by default. To disable this, set the gfm flag to false:

{
  markdown: {
    gfm: false,
  }
}

Type: boolean
Default: true

Astro uses the SmartyPants formatter by default. To disable this, set the smartypants flag to false:

{
  markdown: {
    smartypants: false,
  }
}

Type: RemarkRehype

Pass options to remark-rehype.

{
  markdown: {
    // Example: Translate the footnotes text to another language, here are the default English values
    remarkRehype: { footnoteLabel: "Footnotes", footnoteBackLabel: "Back to content"},
  },
};

Extend Astro with custom integrations. Integrations are your one-stop-shop for adding framework support (like Solid.js), new features (like sitemaps), and new libraries (like Partytown and Turbolinks).

Read our Integrations Guide for help getting started with Astro Integrations.

import react from '@astrojs/react';
import tailwind from '@astrojs/tailwind';
{
  // Example: Add React + Tailwind support to Astro
  integrations: [react(), tailwind()]
}

Pass additional configuration options to Vite. Useful when Astro doesn’t support some advanced configuration that you may need.

View the full vite configuration object documentation on vitejs.dev.

{
  vite: {
    ssr: {
      // Example: Force a broken package to skip SSR processing, if needed
      external: ['broken-npm-package'],
    }
  }
}

{
  vite: {
    // Example: Add custom vite plugins directly to your Astro project
    plugins: [myPlugin()],
  }
}

To help some users migrate between versions of Astro, we occasionally introduce legacy flags. These flags allow you to opt in to some deprecated or otherwise outdated behavior of Astro in the latest version, so that you can continue to upgrade and take advantage of new Astro releases.

Astro offers experimental flags to give users early access to new features. These flags are not guaranteed to be stable.

Type: boolean
Default: false

Enable experimental support for optimizing and resizing images. With this enabled, a new astro:assets module will be exposed.

To enable this feature, set experimental.assets to true in your Astro config:

{
  experimental: {
    assets: true,
  },
}

Type: boolean
Default: false

Enable experimental support for the <ViewTransitions / > component. With this enabled you can opt-in to view transitions on a per-page basis using this component and enable animations with the transition:animate directive.

{
  experimental: {
    viewTransitions: true,
  },
}

Type: boolean
Default: false

Prevents unused components’ scripts from being included in a page unexpectedly. The optimization is best-effort and may inversely miss including the used scripts. Make sure to double-check your built pages before publishing. Enable hoisted script analysis optimization by adding the experimental flag:

{
  experimental: {
    optimizeHoistedScript: true,
  },
}