API Reference

The Astro global is available in all contexts in .astro files. It has the following functions:

Astro.glob() is a way to load many local files into your static site setup.

---
const posts = await Astro.glob('../pages/post/*.md'); // returns an array of posts that live at ./src/pages/post/*.md
---

<div>
{posts.slice(0, 3).map((post) => (
  <article>
    <h1>{post.frontmatter.title}</h1>
    <p>{post.frontmatter.description}</p>
    <a href={post.url}>Read more</a>
  </article>
))}
</div>

.glob() only takes one parameter: a relative URL glob of which local files you’d like to import. It’s asynchronous, and returns an array of the exports from matching files.

.glob() can’t take variables or strings that interpolate them, as they aren’t statically analyzable. (See the troubleshooting guide for a workaround.) This is because Astro.glob() is a wrapper of Vite’s import.meta.glob().

Markdown files have the following interface:

export interface MarkdownInstance<T extends Record<string, any>> {
  /* Any data specified in this file's YAML frontmatter */
  frontmatter: T;
  /* The file path of this file */
  file: string;
  /* The rendered path of this file */
  url: string | undefined;
  /* Astro Component that renders the contents of this file */
  Content: AstroComponent;
  /* Function that returns an array of the h1...h6 elements in this file */
  getHeadings(): Promise<{ depth: number; slug: string; text: string }[]>;
}

You can optionally provide a type for the frontmatter variable using a TypeScript generic.

---
interface Frontmatter {
  title: string;
  description?: string;
}
const posts = await Astro.glob<Frontmatter>('../pages/post/*.md');
---

<ul>
  {posts.map(post => <li>{post.frontmatter.title}</li>)}
</ul>

Astro files have the following interface:

export interface AstroInstance {
  /* The file path of this file */
  file: string;
  /* The URL for this file (if it is in the pages directory) */
  url: string | undefined;
  default: AstroComponent;
}

Other files may have various different interfaces, but Astro.glob() accepts a TypeScript generic if you know exactly what an unrecognized file type contains.

---
interface CustomDataFile {
  default: Record<string, any>;
}
const data = await Astro.glob<CustomDataFile>('../data/**/*.js');
---

Astro.props is an object containing any values that have been passed as component attributes. Layout components for .md and .mdx files receive frontmatter values as props.

---
const { title, date } = Astro.props;
---
<div>
  <h1>{title}</h1>
  <p>{date}</p>
</div>

---
import Heading from '../components/Heading.astro';
---
<Heading title="My First Post" date="09 Aug 2022" />

📚 Learn more about how Markdown and MDX Layouts handle props.

📚 Learn how to add Typescript type definitions for your props.

Astro.params is an object containing the values of dynamic route segments matched for this request.

In static builds, this will be the params returned by getStaticPaths() used for prerendering dynamic routes.

In SSR builds, this can be any value matching the path segments in the dynamic route pattern.

---
export function getStaticPaths() {
  return [
    { params: { id: '1' } },
    { params: { id: '2' } },
    { params: { id: '3' } }
  ];
}

const { id } = Astro.params;
---
<h1>{id}</h1>

See also: params

Astro.request is a standard Request object. It can be used to get the url, headers, method, and even body of the request.

<p>Received a {Astro.request.method} request to "{Astro.request.url}".</p>
<p>Received request headers: <code>{JSON.stringify(Object.fromEntries(Astro.request.headers))}</code>

See also: Astro.url

Astro.response is a standard ResponseInit object. It is used to set the status, statusText, and headers for a page’s response.

---
if(condition) {
  Astro.response.status = 404;
  Astro.response.statusText = 'Not found';
}
---

Or to set a header:

---
Astro.response.headers.set('Set-Cookie', 'a=b; Path=/;');
---

Astro.cookies contains utilities for reading and manipulating cookies.

Getting a cookie via Astro.cookies.get() returns a AstroCookie type. It has the following structure.

The canonical URL of the current page.

A URL object constructed from the current Astro.request.url URL string value. Useful for interacting with individual properties of the request URL, like pathname and origin.

Equivalent to doing new URL(Astro.request.url).

<h1>The current URL is: {Astro.url}</h1>
<h1>The current URL pathname is: {Astro.url.pathname}</h1>
<h1>The current URL origin is: {Astro.url.origin}</h1>

You can also use Astro.url to create new URLs by passing it as an argument to new URL().

---
// Example: Construct a canonical URL using your production domain
const canonicalURL = new URL(Astro.url.pathname, Astro.site);
// Example: Construct a URL for SEO meta tags using your current domain
const socialImageURL = new URL('/images/preview.png', Astro.url);
---
<link rel="canonical" href={canonicalURL} />
<meta property="og:image" content={socialImageURL} />

Specifies the IP address of the request. This property is only available when building for SSR (server-side rendering) and should not be used for static sites.

---
const ip = Astro.clientAddress;
---

<div>Your IP address is: <span class="address">{ ip }</span></div>

Astro.site returns a URL made from site in your Astro config. If undefined, this will return a URL generated from localhost.

Astro.generator is a convenient way to add a <meta name="generator"> tag with your current version of Astro. It follows the format "Astro v1.x.x".

<html>
  <head>
    <meta name="generator" content={Astro.generator} />
  </head>
  <body>
    <footer>
      <p>Built with <a href="https://astro.build">{Astro.generator}</a></p>
    </footer>
  </body>
</html>

Astro.slots contains utility functions for modifying an Astro component’s slotted children.

Type: (slotName: string) => boolean

You can check whether content for a specific slot name exists with Astro.slots.has(). This can be useful when you want to wrap slot contents, but only want to render the wrapper elements when the slot is being used.

---
---
<slot />

{Astro.slots.has('more') && (
  <aside>
    <h2>More</h2>
    <slot name="more" />
  </aside>
)}

Type: (slotName: string, args?: any[]) => Promise<string>

You can asychronously render the contents of a slot to a string of HTML using Astro.slots.render().

---
const html = await Astro.slots.render('default');
---
<Fragment set:html={html} />

Astro.slots.render() optionally accepts a second argument: an array of parameters that will be forwarded to any function children. This can be useful for custom utility components.

For example, this <Shout /> component converts its message prop to uppercase and passes it to the default slot:

---
const message = Astro.props.message.toUpperCase();
let html = '';
if (Astro.slots.has('default')) {
  html = await Astro.slots.render('default', [message]);
}
---
<Fragment set:html={html} />

A callback function passed as <Shout />’s child will receive the all-caps message parameter:

---
import Shout from "../components/Shout.astro";
---
<Shout message="slots!">
  {(message) => <div>{message}</div>}
</Shout>

<!-- renders as <div>SLOTS!</div> -->

Astro.self allows Astro components to be recursively called. This behaviour lets you render an Astro component from within itself by using <Astro.self> in the component template. This can be helpful for iterating over large data stores and nested data-structures.

---
const { items } = Astro.props;
---
<ul class="nested-list">
  {items.map((item) => (
    <li>
      <!-- If there is a nested data-structure we render `<Astro.self>` -->
      <!-- and can pass props through with the recursive call -->
      {Array.isArray(item) ? (
        <Astro.self items={item} />
      ) : (
        item
      )}
    </li>
  ))}
</ul>

This component could then be used like this:

---
import NestedList from './NestedList.astro';
---
<NestedList items={['A', ['B', 'C'], 'D']} />

And would render HTML like this:

<ul class="nested-list">
  <li>A</li>
  <li>
    <ul class="nested-list">
      <li>B</li>
      <li>C</li>
    </ul>
  </li>
  <li>D</li>
</ul>

Endpoint functions receive a context object as the first parameter. It mirrors many of the Astro global properties.

import type { APIContext } from 'astro';

export function get(context: APIContext) {
  // ...
}

context.params is an object containing the values of dynamic route segments matched for this request.

In static builds, this will be the params returned by getStaticPaths() used for prerendering dynamic routes.

In SSR builds, this can be any value matching the path segments in the dynamic route pattern.

import type { APIContext } from 'astro';

export function getStaticPaths() {
  return [
    { params: { id: '1' } },
    { params: { id: '2' } },
    { params: { id: '3' } }
  ];
}

export function get({ params }: APIContext) {
  return {
    body: JSON.stringify({ id: params.id })
  };
}

See also: params

context.props is an object containing any props passed from getStaticPaths(). Because getStaticPaths() is not used when building for SSR (server-side rendering), context.props is only available in static builds.

import type { APIContext } from 'astro';

export function getStaticPaths() {
  return [
    { params: { id: '1' }, props: { author: 'Blu' } },
    { params: { id: '2' }, props: { author: 'Erika' } },
    { params: { id: '3' }, props: { author: 'Matthew' } }
  ];
}

export function get({ props }: APIContext) {
  return {
    body: JSON.stringify({ author: props.author }),
  };
}

See also: Data Passing with props

A standard Request object. It can be used to get the url, headers, method, and even body of the request.

import type { APIContext } from 'astro';

export function get({ request }: APIContext) {
  return {
    body: `Hello ${request.url}`
  }
}

See also: Astro.request

context.cookies contains utilities for reading and manipulating cookies.

See also: Astro.cookies

A URL object constructed from the current context.request.url URL string value.

See also: Astro.url

Specifies the IP address of the request. This property is only available when building for SSR (server-side rendering) and should not be used for static sites.

import type { APIContext } from 'astro';

export function get({ clientAddress }: APIContext) {
  return {
    body: `Your IP address is: ${clientAddress}`
  }
}

See also: Astro.clientAddress

context.site returns a URL made from site in your Astro config. If undefined, this will return a URL generated from localhost.

See also: Astro.site

context.generator is a convenient way to indicate the version of Astro your project is running. It follows the format "Astro v1.x.x".

import type { APIContext } from 'astro';

export function get({ generator, site }: APIContext) {
  const body = JSON.stringify({ generator, site });
  return new Response(body);
}

See also: Astro.generator

context.redirect() returns a Response object that allows you to redirect to another page. This function is only available when building for SSR (server-side rendering) and should not be used for static sites.

import type { APIContext } from 'astro';

export function get({ redirect }: APIContext) {
  return redirect('/login', 302);
}

See also: Astro.redirect

If a page uses dynamic params in the filename, that component will need to export a getStaticPaths() function.

This function is required because Astro is a static site builder. That means that your entire site is built ahead of time. If Astro doesn’t know to generate a page at build time, your users won’t see it when they visit your site.

---
export async function getStaticPaths() {
  return [
    { params: { /* required */ }, props: { /* optional */ } },
    { params: { ... } },
    { params: { ... } },
    // ...
  ];
}
---
<!-- Your HTML template here. -->

The getStaticPaths() function should return an array of objects to determine which paths will be pre-rendered by Astro.

It can also be used in static file endpoints for dynamic routing.

The params key of every returned object tells Astro what routes to build. The returned params must map back to the dynamic parameters and rest parameters defined in your component filepath.

params are encoded into the URL, so only strings are supported as values. The value for each params object must match the parameters used in the page name.

For example, suppose that you have a page at src/pages/posts/[id].astro. If you export getStaticPaths from this page and return the following for paths:

---
export async function getStaticPaths() {
  return [
    { params: { id: '1' } },
    { params: { id: '2' } },
    { params: { id: '3' } }
  ];
}

const { id } = Astro.params;
---
<h1>{id}</h1>

Then Astro will statically generate posts/1, posts/2, and posts/3 at build time.

To pass additional data to each generated page, you can also set a props value on every returned path object. Unlike params, props are not encoded into the URL and so aren’t limited to only strings.

For example, suppose that you generate pages based off of data fetched from a remote API. You can pass the full data object to the page component inside of getStaticPaths:

---
export async function getStaticPaths() {
  const data = await fetch('...').then(response => response.json());

  return data.map((post) => {
    return {
      params: { id: post.id },
      props: { post },
    };
  });
}

const { id } = Astro.params;
const { post } = Astro.props;
---
<h1>{id}: {post.name}</h1>

You can also pass a regular array, which may be helpful when generating or stubbing a known list of routes.

---
export async function getStaticPaths() {
  const posts = [
    {id: '1', category: "astro", title: "API Reference"},
    {id: '2', category: "react", title: "Creating a React Counter!"}
  ];
  return posts.map((post) => {
    return {
      params: { id: post.id },
      props: { post }
    };
  });
}
const {id} = Astro.params;
const {post} = Astro.props;
---
<body>
  <h1>{id}: {post.title}</h1>
  <h2>Category: {post.category}</h2>
</body>

Then Astro will statically generate posts/1 and posts/2 at build time using the page component in pages/posts/[id].astro. The page can reference this data using Astro.props:

Pagination is a common use-case for websites that Astro natively supports via the paginate() function. paginate() will automatically generate the array to return from getStaticPaths() that creates one URL for every page of the paginated collection. The page number will be passed as a param, and the page data will be passed as a page prop.

export async function getStaticPaths({ paginate }) {
  // Load your data with fetch(), Astro.glob(), etc.
  const response = await fetch(`https://pokeapi.co/api/v2/pokemon?limit=150`);
  const result = await response.json();
  const allPokemon = result.results;

  // Return a paginated collection of paths for all posts
  return paginate(allPokemon, { pageSize: 10 });
}

// If set up correctly, The page prop now has everything that
// you need to render a single page (see next section).
const { page } = Astro.props;

paginate() assumes a file name of [page].astro or [...page].astro. The page param becomes the page number in your URL:

• /posts/[page].astro would generate the URLs /posts/1, /posts/2, /posts/3, etc.
• /posts/[...page].astro would generate the URLs /posts, /posts/2, /posts/3, etc.

Pagination will pass a page prop to every rendered page that represents a single page of data in the paginated collection. This includes the data that you’ve paginated (page.data) as well as metadata for the page (page.url, page.start, page.end, page.total, etc). This metadata is useful for things like a “Next Page” button or a “Showing 1-10 of 100” message.

All ESM modules include a import.meta property. Astro adds import.meta.env through Vite.

import.meta.env.SSR can be used to know when rendering on the server. Sometimes you might want different logic, for example a component that should only be rendered in the client:

import { h } from 'preact';

export default function () {
  return import.meta.env.SSR ? <div class="spinner"></div> : <FancyComponent />;
}

Astro includes several built-in components for you to use in your projects. All built-in components are available in .astro files via import {} from 'astro/components';.

The Markdown component is no longer built into Astro. See how to import Markdown into your Astro files on our Markdown page.

---
import { Code } from 'astro/components';
---
<!-- Syntax highlight some JavaScript code. -->
<Code code={`const foo = 'bar';`} lang="js" />
<!-- Optional: customize your theme. -->
<Code code={`const foo = 'bar';`} lang="js" theme="dark-plus" />
<!-- Optional: Enable word wrapping. -->
<Code code={`const foo = 'bar';`} lang="js" wrap />

This component provides syntax highlighting for code blocks at build time (no client-side JavaScript included). The component is powered internally by Shiki and it supports all popular themes and languages. Plus, you can add your custom themes and languages by passing them to theme and lang respectively.

To use the Prism highlighter component, first install the @astrojs/prism package:

npm install @astrojs/prism

pnpm install @astrojs/prism

yarn add @astrojs/prism

---
import { Prism } from '@astrojs/prism';
---
<Prism lang="js" code={`const foo = 'bar';`} />

This component provides language-specific syntax highlighting for code blocks by applying Prism’s CSS classes. Note that you need to provide a Prism CSS stylesheet (or bring your own) for syntax highlighting to appear! See the Prism configuration section for more details.

See the list of languages supported by Prism where you can find a language’s corresponding alias. And, you can also display your Astro code blocks with lang="astro"!

---
import { Debug } from 'astro/components';
const serverObject = {
  a: 0,
  b: "string",
  c: {
    nested: "object"
  }
}
---
<Debug {serverObject} />

This component provides a way to inspect values on the client-side, without any JavaScript.