Astro Runtime API

Astro global

Section titled Astro global

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

Astro.glob()

Section titled Astro.glob()

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

src/components/my-component.astro

---
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>
    <h2>{post.frontmatter.title}</h2>
    <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().

Note

You can also use import.meta.glob() itself in your Astro project. You may want to do this when:

• You need this feature in a file that isn’t .astro, like an API route. Astro.glob() is only available in .astro files, while import.meta.glob() is available anywhere in the project.
• You don’t want to load each file immediately. import.meta.glob() can return functions that import the file content, rather than returning the content itself. Note that this import includes all styles and scripts for any imported files. These will be bundled and added to the page whether or not a file is actually used, as this is decided by static analysis, not at runtime.
• You want access to each file’s path. import.meta.glob() returns a map of a file’s path to its content, while Astro.glob() returns a list of content.
• You want to pass multiple patterns; for example, you want to add a “negative pattern” that filters out certain files. import.meta.glob() can optionally take an array of glob strings, rather than a single string.

Read more in the Vite documentation.

Markdown Files

Section titled Markdown Files

Markdown files loaded with Astro.glob() return the following MarkdownInstance interface:

export interface MarkdownInstance<T extends Record<string, any>> {
  /* Any data specified in this file's YAML frontmatter */
  frontmatter: T;
  /* The absolute 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: AstroComponentFactory;
  /** (Markdown only) Raw Markdown file content, excluding layout HTML and YAML frontmatter */
  rawContent(): string;
  /** (Markdown only) Markdown file compiled to HTML, excluding layout HTML */
  compiledContent(): string;
  /* Function that returns an array of the h1...h6 elements in this file */
  getHeadings(): Promise<{ depth: number; slug: string; text: string }[]>;
  default: AstroComponentFactory;
}

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

Section titled Astro Files

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: AstroComponentFactory;
}

Other Files

Section titled Other Files

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

Section titled Astro.props

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.

src/components/Heading.astro

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

src/pages/index.astro

---
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

Section titled Astro.params

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.

src/pages/posts/[id].astro

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

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

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

src/pages/posts/[id].astro

---
import { getPost } from '../api';

const post = await getPost(Astro.params.id);

// No posts found with this ID
if (!post) {
  Astro.redirect("/404")
}
---
<html>
  <h1>{post.name}</h1>
</html>

See also: params

Astro.request

Section titled Astro.request

Type: Request

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

Note

With the default output: 'static' option, Astro.request.url does not contain search parameters, like ?foo=bar, as it’s not possible to determine them ahead of time during static builds. However in output: 'server' mode, Astro.request.url does contain search parameters as it can be determined from a server request.

Astro.response

Section titled Astro.response

Type: ResponseInit & { readonly headers: Headers }

Astro.response is a standard ResponseInit object. It has the following structure.

• status: The numeric status code of the response, e.g., 200.
• statusText: The status message associated with the status code, e.g., 'OK'.
• headers: A Headers instance that you can use to set the HTTP headers of the response.

Astro.response 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

Section titled Astro.cookies

Type: AstroCookies

Added in: astro@1.4.0

Astro.cookies contains utilities for reading and manipulating cookies in server-side rendering mode.

get

Section titled get

Type: (key: string, options?: AstroCookieGetOptions) => AstroCookie | undefined

Gets the cookie as an AstroCookie object, which contains the value and utility functions for converting the cookie to non-string types.

has

Section titled has

Type: (key: string, options?: AstroCookieGetOptions) => boolean

Whether this cookie exists. If the cookie has been set via Astro.cookies.set() this will return true, otherwise it will check cookies in the Astro.request.

set

Section titled set

Type: (key: string, value: string | object, options?: AstroCookieSetOptions) => void

Sets the cookie key to the given value. This will attempt to convert the cookie value to a string. Options provide ways to set cookie features, such as the maxAge or httpOnly.

delete

Section titled delete

Type: (key: string, options?: AstroCookieDeleteOptions) => void

Invalidates a cookie by setting the expiration date in the past (0 in Unix time).

Once a cookie is “deleted” (expired), Astro.cookies.has() will return false and Astro.cookies.get() will return an AstroCookie with a value of undefined. Options available when deleting a cookie are: domain, path, httpOnly, sameSite, and secure.

merge

Section titled merge

Type: (cookies: AstroCookies) => void

Merges a new AstroCookies instance into the current instance. Any new cookies will be added to the current instance and any cookies with the same name will overwrite existing values.

headers

Section titled headers

Type: () => Iterator<string>

Gets the header values for Set-Cookie that will be sent out with the response.

AstroCookie

Section titled AstroCookie

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

value

Section titled value

Type: string

The raw string value of the cookie.

json

Section titled json

Type: () => Record<string, any>

Parses the cookie value via JSON.parse(), returning an object. Throws if the cookie value is not valid JSON.

number

Section titled number

Type: () => number

Parses the cookie value as a Number. Returns NaN if not a valid number.

boolean

Section titled boolean

Type: () => boolean

Converts the cookie value to a boolean.

AstroCookieGetOptions

Section titled AstroCookieGetOptions

Added in: astro@4.1.0

Getting a cookie also allows specifying options via the AstroCookieGetOptions interface:

decode

Section titled decode

Type: (value: string) => string

Allows customization of how a cookie is deserialized into a value.

AstroCookieSetOptions

Section titled AstroCookieSetOptions

Added in: astro@4.1.0

Setting a cookie via Astro.cookies.set() allows passing in a AstroCookieSetOptions to customize how the cookie is serialized.

domain

Section titled domain

Type: string

Specifies the domain. If no domain is set, most clients will interpret to apply to the current domain.

expires

Section titled expires

Type: Date

Specifies the date on which the cookie will expire.

httpOnly

Section titled httpOnly

Type: boolean

If true, the cookie will not be accessible client-side.

maxAge

Section titled maxAge

Type: number

Specifies a number, in seconds, for which the cookie is valid.

path

Section titled path

Type: string

Specifies a subpath of the domain in which the cookie is applied.

sameSite

Section titled sameSite

Type: boolean | 'lax' | 'none' | 'strict'

Specifies the value of the SameSite cookie header.

secure

Section titled secure

Type: boolean

If true, the cookie is only set on https sites.

encode

Section titled encode

Type: (value: string) => string

Allows customizing how the cookie is serialized.

Astro.redirect()

Section titled Astro.redirect()

Type: (path: string, status?: number) => Response

Allows you to redirect to another page, and optionally provide an HTTP response status code as a second parameter.

A page (and not a child component) must return the result of Astro.redirect() for the redirect to occur.

For statically-generated sites, this will produce a client redirect using a <meta http-equiv="refresh"> tag and does not support status codes.

When using an on-demand rendering mode, status codes are supported. Astro will serve redirected requests with a default HTTP response status of 302 unless another code is specified.

The following example redirects a user to a login page:

src/pages/account.astro

---
import { isLoggedIn } from '../utils';

const cookie = Astro.request.headers.get('cookie');

// If the user is not logged in, redirect them to the login page
if (!isLoggedIn(cookie)) {
  return Astro.redirect('/login');
}
---

Astro.rewrite()

Section titled Astro.rewrite()

Type: (rewritePayload: string | URL | Request) => Promise<Response>

Added in: astro@4.13.0

Allows you to serve content from a different URL or path without redirecting the browser to a new page.

The method accepts either a string, a URL, or a Request for the location of the path.

Use a string to provide an explicit path:

src/pages/index.astro

---
return Astro.rewrite("/login")
---

Use a URL type when you need to construct the URL path for the rewrite. The following example renders a page’s parent path by creating a new URL from the relative "../" path:

src/pages/blog/index.astro

---
return Astro.rewrite(new URL("../", Astro.url))
---

Use a Request type for complete control of the Request sent to the server for the new path. The following example sends a request to render the parent page while also providing headers:

src/pages/blog/index.astro

---
return Astro.rewrite(new Request(new URL("../", Astro.url), {
  headers: {
    "x-custom-header": JSON.stringify(Astro.locals.someValue)
  }
}))
---

Astro.url

Section titled Astro.url

Type: URL

Added in: astro@1.0.0-rc

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).

Astro.url will be localhost in dev mode if site is not configured for static sites, and for on-demand rendered sites using server or hybrid output.

<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().

src/pages/index.astro

---
// 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} />

Astro.clientAddress

Section titled Astro.clientAddress

Type: string

Added in: astro@1.0.0-rc

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

Section titled Astro.site

Type: URL | undefined

Astro.site returns a URL made from site in your Astro config. If site in your Astro config isn’t defined, Astro.site won’t be defined.

Astro.generator

Section titled Astro.generator

Type: string

Added in: astro@1.0.0

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

Section titled Astro.slots

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

Astro.slots.has()

Section titled Astro.slots.has()

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.

src/pages/index.astro

---
---
<slot />

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

Astro.slots.render()

Section titled Astro.slots.render()

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

You can asynchronously 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} />

Note

This is for advanced use cases! In most circumstances, it is simpler to render slot contents with the <slot /> element.

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:

src/components/Shout.astro

---
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:

src/pages/index.astro

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

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

Callback functions can be passed to named slots inside a wrapping HTML element tag with a slot attribute. This element is only used to transfer the callback to a named slot and will not be rendered onto the page.

<Shout message="slots!">
  <fragment slot="message">
    {(message) => <div>{message}</div>}
  </fragment>
</Shout>

Use a standard HTML element for the wrapping tag, or any lower case tag (e.g. <fragment> instead of <Fragment />) that will not be interpreted as a component. Do not use the HTML <slot> element as this will be interpreted as an Astro slot.

Astro.self

Section titled Astro.self

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.

NestedList.astro

---
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>

Astro.locals

Section titled Astro.locals

Added in: astro@2.4.0

Astro.locals is an object containing any values from the context.locals object from a middleware. Use this to access data returned by middleware in your .astro files.

src/pages/Orders.astro

---
const title = Astro.locals.welcomeTitle();
const orders = Array.from(Astro.locals.orders.entries());
---
<h1>{title}</h1>
<ul>
    {orders.map(order => {
        return <li>{/* do something with each order */}</li>
    })}
</ul>

Astro.preferredLocale

Section titled Astro.preferredLocale

Type: string | undefined

Added in: astro@3.5.0

Astro.preferredLocale is a computed value that represents the preferred locale of the user.

It is computed by checking the configured locales in your i18n.locales array and locales supported by the users’s browser via the header Accept-Language. This value is undefined if no such match exists.

This property is only available when building for SSR (server-side rendering) and should not be used for static sites.

Astro.preferredLocaleList

Section titled Astro.preferredLocaleList

Type: string[] | undefined

Added in: astro@3.5.0

Astro.preferredLocaleList represents the array of all locales that are both requested by the browser and supported by your website. This produces a list of all compatible languages between your site and your visitor.

If none of the browser’s requested languages are found in your locales array, then the value is []: you do not support any of your visitor’s preferred locales.

If the browser does not specify any preferred languages, then this value will be i18n.locales: all of your supported locales will be considered equally preferred by a visitor with no preferences.

This property is only available when building for SSR (server-side rendering) and should not be used for static sites.

Astro.currentLocale

Section titled Astro.currentLocale

Type: string | undefined

Added in: astro@3.5.6

The locale computed from the current URL, using the syntax specified in your locales configuration. If the URL does not contain a /[locale]/ prefix, then the value will default to i18n.defaultLocale.

Astro.getActionResult()

Section titled Astro.getActionResult()

Type: (action: TAction) => ActionReturnType<TAction> | undefined

Added in: astro@4.15.0

Astro.getActionResult() is a function that returns the result of an Action submission. This accepts an action function as an argument (e.g. actions.logout) and returns a data or error object when a submission is received. Otherwise, it will return undefined.

src/pages/index.astro

---
import { actions } from 'astro:actions';

const result = Astro.getActionResult(actions.logout);
---

<form action={actions.logout}>
  <button type="submit">Log out</button>
</form>
{result?.error && <p>Failed to log out. Please try again.</p>}

Astro.callAction()

Section titled Astro.callAction()

Added in: astro@4.15.0

Astro.callAction() is a function used to call an Action handler directly from your Astro component. This function accepts an Action function as the first argument (e.g. actions.logout) and any input that action receives as the second argument. It returns the result of the action as a promise.

src/pages/index.astro

---
import { actions } from 'astro:actions';

const { data, error } = await Astro.callAction(actions.logout, { userId: '123' });
---

Endpoint Context

Section titled Endpoint Context

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

endpoint.json.ts

import type { APIContext } from 'astro';

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

context.params

Section titled context.params

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.

src/pages/posts/[id].json.ts

import type { APIContext } from 'astro';

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

export function GET({ params }: APIContext) {
  return new Response(
    JSON.stringify({ id: params.id }),
  );
}

See also: params

context.props

Section titled context.props

Added in: astro@1.5.0

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.

src/pages/posts/[id].json.ts

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 new Response(
    JSON.stringify({ author: props.author }),
  );
}

See also: Data Passing with props

context.request

Section titled context.request

Type: Request

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 new Response(`Hello ${request.url}`);
}

See also: Astro.request

context.cookies

Section titled context.cookies

Type: AstroCookies

context.cookies contains utilities for reading and manipulating cookies.

See also: Astro.cookies

context.url

Section titled context.url

Type: URL

Added in: astro@1.5.0

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

See also: Astro.url

context.clientAddress

Section titled context.clientAddress

Type: string

Added in: astro@1.5.0

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 new Response(`Your IP address is: ${clientAddress}`);
}

See also: Astro.clientAddress

context.site

Section titled context.site

Type: URL | undefined

Added in: astro@1.5.0

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

Section titled context.generator

Type: string

Added in: astro@1.5.0

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

src/pages/site-info.json.ts

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()

Section titled context.redirect()

Type: (path: string, status?: number) => Response

Added in: astro@1.5.0

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()

context.rewrite()

Section titled context.rewrite()

Type: (rewritePayload: string | URL | Request) => Promise<Response>

Added in: astro@4.13.0

Allows you to serve content from a different URL or path without redirecting the browser to a new page.

The method accepts either a string, a URL, or a Request for the location of the path.

Use a string to provide an explicit path:

import type { APIContext } from 'astro';

export function GET({ rewrite }: APIContext) {
  return rewrite('/login');
}

Use a URL type when you need to construct the URL path for the rewrite. The following example renders a page’s parent path by creating a new URL from the relative "../" path:

import type { APIContext } from 'astro';

export function GET({ rewrite }: APIContext) {
  return rewrite(new URL("../", Astro.url));
}

Use a Request type for complete control of the Request sent to the server for the new path. The following example sends a request to render the parent page while also providing headers:

import type { APIContext } from 'astro';

export function GET({ rewrite }: APIContext) {
  return rewrite(new Request(new URL("../", Astro.url), {
   headers: {
     "x-custom-header": JSON.stringify(Astro.locals.someValue)
   }
 }));
}

See also: Astro.rewrite()

context.locals

Section titled context.locals

Added in: astro@2.4.0

context.locals is an object used to store and access arbitrary information during the lifecycle of a request.

Middleware functions can read and write the values of context.locals:

src/middleware.ts

import type { MiddlewareHandler } from 'astro';

export const onRequest: MiddlewareHandler = ({ locals }, next) => {
  if (!locals.title) {
    locals.title = "Default Title";
  }
  return next();
}

API endpoints can only read information from context.locals:

src/pages/hello.ts

import type { APIContext } from 'astro';

export function GET({ locals }: APIContext) {
  return new Response(locals.title); // "Default Title"
}

See also: Astro.locals

context.getActionResult()

Section titled context.getActionResult()

Type: (action: TAction) => ActionReturnType<TAction> | undefined

Added in: astro@4.15.0

context.getActionResult() is a function that returns the result of an Action submission. This accepts an action function as an argument (e.g. actions.logout), and returns a data or error object when a submission is received. Otherwise, it will return undefined.

See also Astro.getActionResult()

context.callAction()

Section titled context.callAction()

Added in: astro@4.15.0

context.callAction() is a function used to call an Action handler directly from your Astro component. This function accepts an Action function as the first argument (e.g. actions.logout) and any input that action receives as the second argument. It returns the result of the action as a promise.

See also Astro.callAction()

getStaticPaths()

Section titled getStaticPaths()

Type: (options: GetStaticPathsOptions) => Promise<GetStaticPathsResult> | GetStaticPathsResult

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.

Tip

When using TypeScript, use the GetStaticPaths type utility to ensure type-safe access of your params and props.

Caution

The getStaticPaths() function executes in its own isolated scope once, before any page loads. Therefore you can’t reference anything from its parent scope, other than file imports. The compiler will warn if you break this requirement.

params

Section titled params

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.

Data Passing with props

Section titled Data Passing with props

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:

paginate()

Section titled paginate()

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() has the following arguments:

• data - array containing the page’s data passed to the paginate() function
• options - Optional object with the following properties:
  • pageSize - The number of items shown per page (10 by default)
  • params - Send additional parameters for creating dynamic routes
  • props - Send additional props to be available on each page

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.

The pagination page prop

Section titled The pagination page prop

Type: Page<TData>

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.

page.data

Section titled page.data

Type: Array<TData>

Array of data returned from the paginate() function for the current page.

page.start

Section titled page.start

Type: number

Index of first item on current page, starting at 0. (e.g. if pageSize: 25, this would be 0 on page 1, 25 on page 2, etc.)

page.end

Section titled page.end

Type: number

Index of last item on current page.

page.size

Section titled page.size

Type: number
Default: 10

How many items per-page.

page.total

Section titled page.total

Type: number

The total number of items across all pages.

page.currentPage

Section titled page.currentPage

Type: number

The current page number, starting with 1.

page.lastPage

Section titled page.lastPage

Type: number

The total number of pages.

page.url.current

Section titled page.url.current

Type: string

Get the URL of the current page (useful for canonical URLs).

page.url.prev

Section titled page.url.prev

Type: string | undefined

Get the URL of the previous page (will be undefined if on page 1). If a value is set for base, prepend the base path to the URL.

page.url.next

Section titled page.url.next

Type: string | undefined

Get the URL of the next page (will be undefined if no more pages). If a value is set for base, prepend the base path to the URL.

page.url.first

Section titled page.url.first

Type: string | undefined

Added in: astro@4.12.0

Get the URL of the first page (will be undefined if on page 1). If a value is set for base, prepend the base path to the URL.

page.url.last

Section titled page.url.last

Type: string | undefined

Added in: astro@4.12.0

Get the URL of the last page (will be undefined if no more pages). If a value is set for base, prepend the base path to the URL.

import.meta

Section titled import.meta

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, like a component that should only be rendered in the client:

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