Modules

SvelteKit makes a number of modules available to your application.

$app/environmentpermalink

ts
import { browser, building, dev, version } from '$app/environment';

browserpermalink

true if the app is running in the browser.

ts
const browser: boolean;

buildingpermalink

SvelteKit analyses your app during the build step by running it. During this process, building is true. This also applies during prerendering.

ts
const building: boolean;

devpermalink

Whether the dev server is running. This is not guaranteed to correspond to NODE_ENV or MODE.

ts
const dev: boolean;

versionpermalink

The value of config.kit.version.name.

ts
const version: string;

$app/formspermalink

ts
import { applyAction, deserialize, enhance } from '$app/forms';

applyActionpermalink

This action updates the form property of the current page with the given data and updates $page.status. In case of an error, it redirects to the nearest error page.

ts
function applyAction<
  Success extends Record<string, unknown> | undefined = Record<string, any>,
  Invalid extends Record<string, unknown> | undefined = Record<string, any>
>(result: ActionResult<Success, Invalid>): Promise<void>;

deserializepermalink

Use this function to deserialize the response from a form submission. Usage:

ts
import { deserialize } from '$app/forms';
 
async function handleSubmit(event) {
  const response = await fetch('/form?/action', {
  method: 'POST',
  body: new FormData(event.target)
  });
 
  const result = deserialize(await response.text());
  // ...
}

ts
function deserialize<
  Success extends Record<string, unknown> | undefined = Record<string, any>,
  Invalid extends Record<string, unknown> | undefined = Record<string, any>
>(serialized: string): ActionResult<Success, Invalid>;

enhancepermalink

This action enhances a <form> element that otherwise would work without JavaScript.

ts
function enhance<
  Success extends Record<string, unknown> | undefined = Record<string, any>,
  Invalid extends Record<string, unknown> | undefined = Record<string, any>
>(
  form: HTMLFormElement,
  /**
   * Called upon submission with the given FormData and the `action` that should be triggered.
   * If `cancel` is called, the form will not be submitted.
   * You can use the abort `controller` to cancel the submission in case another one starts.
   * If a function is returned, that function is called with the response from the server.
   * If nothing is returned, the fallback will be used.
   *
   * If this function or its return value isn't set, it
   * - falls back to updating the `form` prop with the returned data if the action is one same page as the form
   * - updates `$page.status`
   * - resets the `<form>` element and invalidates all data in case of successful submission with no redirect response
   * - redirects in case of a redirect response
   * - redirects to the nearest error page in case of an unexpected error
   *
   * If you provide a custom function with a callback and want to use the default behavior, invoke `update` in your callback.
   */
  submit?: SubmitFunction<Success, Invalid>
): { destroy(): void };

ts
import {
  afterNavigate,
  beforeNavigate,
  disableScrollHandling,
  goto,
  invalidate,
  invalidateAll,
  preloadCode,
  preloadData
} from '$app/navigation';

A lifecycle function that runs the supplied callback when the current component mounts, and also whenever we navigate to a new URL.

afterNavigate must be called during a component initialization. It remains active as long as the component is mounted.

ts
function afterNavigate(callback: (navigation: AfterNavigate) => void): void;

A navigation interceptor that triggers before we navigate to a new URL, whether by clicking a link, calling goto(...), or using the browser back/forward controls. Calling cancel() will prevent the navigation from completing. If the navigation would have directly unloaded the current page, calling cancel will trigger the native browser unload confirmation dialog. In these cases, navigation.willUnload is true.

When a navigation isn't client side, navigation.to.route.id will be null.

beforeNavigate must be called during a component initialization. It remains active as long as the component is mounted.

ts
function beforeNavigate(callback: (navigation: BeforeNavigate) => void): void;

If called when the page is being updated following a navigation (in onMount or afterNavigate or an action, for example), this disables SvelteKit's built-in scroll handling. This is generally discouraged, since it breaks user expectations.

ts
function disableScrollHandling(): void;

Returns a Promise that resolves when SvelteKit navigates (or fails to navigate, in which case the promise rejects) to the specified url. For external URLs, use window.location = url instead of calling goto(url).

ts
function goto(
  url: string | URL,
  opts?: {
    /**
     * If `true`, will replace the current `history` entry rather than creating a new one with `pushState`
     */
    replaceState?: boolean;
    /**
     * If `true`, the browser will maintain its scroll position rather than scrolling to the top of the page after navigation
     */
    noScroll?: boolean;
    /**
     * If `true`, the currently focused element will retain focus after navigation. Otherwise, focus will be reset to the body
     */
    keepFocus?: boolean;
    /**
     * The state of the new/updated history entry
     */
    state?: any;
    /**
     * If `true`, all `load` functions of the page will be rerun. See https://kit.svelte.dev/docs/load#rerunning-load-functions for more info on invalidation.
     */
    invalidateAll?: boolean;
  }
): Promise<void>;

Causes any load functions belonging to the currently active page to re-run if they depend on the url in question, via fetch or depends. Returns a Promise that resolves when the page is subsequently updated.

If the argument is given as a string or URL, it must resolve to the same URL that was passed to fetch or depends (including query parameters). To create a custom identifier, use a string beginning with [a-z]+: (e.g. custom:state) — this is a valid URL.

The function argument can be used define a custom predicate. It receives the full URL and causes load to rerun if true is returned. This can be useful if you want to invalidate based on a pattern instead of a exact match.

ts
// Example: Match '/path' regardless of the query parameters
import { invalidate } from '$app/navigation';
 
invalidate((url) => url.pathname === '/path');

ts
function invalidate(url: string | URL | ((url: URL) => boolean)): Promise<void>;

Causes all load functions belonging to the currently active page to re-run. Returns a Promise that resolves when the page is subsequently updated.

ts
function invalidateAll(): Promise<void>;

Programmatically imports the code for routes that haven't yet been fetched. Typically, you might call this to speed up subsequent navigation.

You can specify routes by any matching pathname such as /about (to match src/routes/about/+page.svelte) or /blog/* (to match src/routes/blog/[slug]/+page.svelte).

Unlike preloadData, this won't call load functions. Returns a Promise that resolves when the modules have been imported.

ts
function preloadCode(...urls: string[]): Promise<void>;

Programmatically preloads the given page, which means

ensuring that the code for the page is loaded, and
calling the page's load function with the appropriate options.

This is the same behaviour that SvelteKit triggers when the user taps or mouses over an <a> element with data-sveltekit-preload-data. If the next navigation is to href, the values returned from load will be used, making navigation instantaneous. Returns a Promise that resolves when the preload is complete.

ts
function preloadData(href: string): Promise<void>;

$app/pathspermalink

ts
import { assets, base } from '$app/paths';

assetspermalink

An absolute path that matches config.kit.paths.assets.

If a value for config.kit.paths.assets is specified, it will be replaced with '/_svelte_kit_assets' during vite dev or vite preview, since the assets don't yet live at their eventual URL.

ts
const assets: `https://${string}` | `http://${string}`;

basepermalink

A string that matches config.kit.paths.base.

Example usage: <a href="{base}/your-page">Link</a>

ts
const base: `/${string}`;

$app/storespermalink

ts
import { getStores, navigating, page, updated } from '$app/stores';

Stores on the server are contextual — they are added to the context of your root component. This means that page is unique to each request, rather than shared between multiple requests handled by the same server simultaneously.

Because of that, you must subscribe to the stores during component initialization (which happens automatically if you reference the store value, e.g. as $page, in a component) before you can use them.

In the browser, we don't need to worry about this, and stores can be accessed from anywhere. Code that will only ever run on the browser can refer to (or subscribe to) any of these stores at any time.

getStorespermalink

A function that returns all of the contextual stores. On the server, this must be called during component initialization. Only use this if you need to defer store subscription until after the component has mounted, for some reason.

ts
function getStores(): {
  navigating: typeof navigating;
  page: typeof page;
  updated: typeof updated;
};

navigatingpermalink

A readable store. When navigating starts, its value is a Navigation object with from, to, type and (if type === 'popstate') delta properties. When navigating finishes, its value reverts to null.

On the server, this store can only be subscribed to during component initialization. In the browser, it can be subscribed to at any time.

ts
const navigating: Readable<Navigation | null>;

pagepermalink

A readable store whose value contains page data.

On the server, this store can only be subscribed to during component initialization. In the browser, it can be subscribed to at any time.

ts
const page: Readable<Page>;

updatedpermalink

A readable store whose initial value is false. If version.pollInterval is a non-zero value, SvelteKit will poll for new versions of the app and update the store value to true when it detects one. updated.check() will force an immediate check, regardless of polling.

On the server, this store can only be subscribed to during component initialization. In the browser, it can be subscribed to at any time.

ts
const updated: Readable<boolean> & { check(): Promise<boolean> };

$env/dynamic/privatepermalink

This module provides access to runtime environment variables, as defined by the platform you're running on. For example if you're using adapter-node (or running vite preview), this is equivalent to process.env. This module only includes variables that do not begin with config.kit.env.publicPrefix.

This module cannot be imported into client-side code.

ts
import { env } from '$env/dynamic/private';
console.log(env.DEPLOYMENT_SPECIFIC_VARIABLE);

In dev, $env/dynamic always includes environment variables from .env. In prod, this behavior will depend on your adapter.

$env/dynamic/publicpermalink

Similar to $env/dynamic/private, but only includes variables that begin with config.kit.env.publicPrefix (which defaults to PUBLIC_), and can therefore safely be exposed to client-side code.

Note that public dynamic environment variables must all be sent from the server to the client, causing larger network requests — when possible, use $env/static/public instead.

ts
import { env } from '$env/dynamic/public';
console.log(env.PUBLIC_DEPLOYMENT_SPECIFIC_VARIABLE);

$env/static/privatepermalink

Environment variables loaded by Vite from .env files and process.env. Like $env/dynamic/private, this module cannot be imported into client-side code. This module only includes variables that do not begin with config.kit.env.publicPrefix.

Unlike $env/dynamic/private, the values exported from this module are statically injected into your bundle at build time, enabling optimisations like dead code elimination.

ts
import { API_KEY } from '$env/static/private';

Note that all environment variables referenced in your code should be declared (for example in an .env file), even if they don't have a value until the app is deployed:

MY_FEATURE_FLAG=""

You can override .env values from the command line like so:

MY_FEATURE_FLAG="enabled" npm run dev

$env/static/publicpermalink

Similar to $env/static/private, except that it only includes environment variables that begin with config.kit.env.publicPrefix (which defaults to PUBLIC_), and can therefore safely be exposed to client-side code.

Values are replaced statically at build time.

ts
import { PUBLIC_BASE_URL } from '$env/static/public';

$libpermalink

This is a simple alias to src/lib, or whatever directory is specified as config.kit.files.lib. It allows you to access common components and utility modules without ../../../../ nonsense.

`$lib/server`permalink

A subdirectory of $lib. SvelteKit will prevent you from importing any modules in $lib/server into client-side code. See server-only modules.

$service-workerpermalink

ts
import { build, files, prerendered, version } from '$service-worker';

This module is only available to service workers.

buildpermalink

An array of URL strings representing the files generated by Vite, suitable for caching with cache.addAll(build). During development, this is an empty array.

ts
const build: string[];

filespermalink

An array of URL strings representing the files in your static directory, or whatever directory is specified by config.kit.files.assets. You can customize which files are included from static directory using config.kit.serviceWorker.files

ts
const files: string[];

prerenderedpermalink

An array of pathnames corresponding to prerendered pages and endpoints. During development, this is an empty array.

ts
const prerendered: string[];

versionpermalink

See config.kit.version. It's useful for generating unique cache names inside your service worker, so that a later deployment of your app can invalidate old caches.

ts
const version: string;

@sveltejs/kitpermalink

ts
import { error, fail, json, redirect, text } from '@sveltejs/kit';

errorpermalink

Creates an HttpError object with an HTTP status code and an optional message. This object, if thrown during request handling, will cause SvelteKit to return an error response without invoking handleError. Make sure you're not catching the thrown error, which would prevent SvelteKit from handling it.

ts
function error(status: number, body: App.Error): HttpError;

errorpermalink

ts
function error(
  status: number,
  // this overload ensures you can omit the argument or pass in a string if App.Error is of type { message: string }
  body?: { message: string } extends App.Error
    ? App.Error | string | undefined
    : never
): HttpError;

failpermalink

Create an ActionFailure object.

ts
function fail<T extends Record<string, unknown> | undefined>(
  status: number,
  data?: T
): ActionFailure<T>;

jsonpermalink

Create a JSON Response object from the supplied data.

ts
function json(data: any, init?: ResponseInit): Response;

redirectpermalink

Create a Redirect object. If thrown during request handling, SvelteKit will return a redirect response. Make sure you're not catching the thrown redirect, which would prevent SvelteKit from handling it.

ts
function redirect(
  status: 300 | 301 | 302 | 303 | 304 | 305 | 306 | 307 | 308,
  location: string
): Redirect;

textpermalink

Create a Response object from the supplied body.

ts
function text(body: string, init?: ResponseInit): Response;

@sveltejs/kit/hookspermalink

ts
import { sequence } from '@sveltejs/kit/hooks';

sequencepermalink

A helper function for sequencing multiple handle calls in a middleware-like manner.

src/hooks.server.js

ts
import { sequence } from '@sveltejs/kit/hooks';
 
Binding element 'html' implicitly has an 'any' type.7031Binding element 'html' implicitly has an 'any' type.async function first({ event, resolve }) {
  console.log('first pre-processing');
  const result = await resolve(event, {
    transformPageChunk: ({ html }) => {
      // transforms are applied in reverse order
      console.log('first transform');
      return html;
    }
  });
  console.log('first post-processing');
Binding element 'event' implicitly has an 'any' type.
Binding element 'resolve' implicitly has an 'any' type.7031
7031Binding element 'event' implicitly has an 'any' type.
Binding element 'resolve' implicitly has an 'any' type.  return result;
}
 
Binding element 'html' implicitly has an 'any' type.7031Binding element 'html' implicitly has an 'any' type.async function second({ event, resolve }) {
  console.log('second pre-processing');
  const result = await resolve(event, {
    transformPageChunk: ({ html }) => {
      console.log('second transform');
      return html;
    }
  });
  console.log('second post-processing');
  return result;
}
 
export const handle = sequence(first, second);

The example above would print:

first pre-processing
second pre-processing
second transform
first transform
second post-processing
first post-processing

ts
function sequence(...handlers: Handle[]): Handle;

@sveltejs/kit/nodepermalink

ts
import { getRequest, setResponse } from '@sveltejs/kit/node';

Utilities used by adapters for Node-like environments.

getRequestpermalink

ts
function getRequest(opts: {
  base: string;
  request: import('http').IncomingMessage;
  bodySizeLimit?: number;
}): Promise<Request>;

setResponsepermalink

ts
function setResponse(
  res: import('http').ServerResponse,
  response: Response
): void;

@sveltejs/kit/node/polyfillspermalink

ts
import { installPolyfills } from '@sveltejs/kit/node/polyfills';

A polyfill for fetch and its related interfaces, used by adapters for environments that don't provide a native implementation.

installPolyfillspermalink

Make various web APIs available as globals:

crypto
fetch
Headers
Request
Response

ts
function installPolyfills(): void;

@sveltejs/kit/vitepermalink

ts
import { sveltekit } from '@sveltejs/kit/vite';

sveltekitpermalink

Returns the SvelteKit Vite plugins.

ts
function sveltekit(): Promise<Plugin[]>;

previous Command Line Interface

next Types

Modules

$app/environmentpermalink

browserpermalink

buildingpermalink

devpermalink

versionpermalink

$app/formspermalink

applyActionpermalink

deserializepermalink

enhancepermalink

$app/navigationpermalink

afterNavigatepermalink

beforeNavigatepermalink

disableScrollHandlingpermalink

gotopermalink

invalidatepermalink

invalidateAllpermalink

preloadCodepermalink

preloadDatapermalink

$app/pathspermalink

assetspermalink

basepermalink

$app/storespermalink

getStorespermalink

navigatingpermalink

pagepermalink

updatedpermalink

$env/dynamic/privatepermalink

$env/dynamic/publicpermalink

$env/static/privatepermalink

$env/static/publicpermalink

$libpermalink

$lib/serverpermalink

$service-workerpermalink

buildpermalink

filespermalink

prerenderedpermalink

versionpermalink

@sveltejs/kitpermalink

errorpermalink

errorpermalink

failpermalink

jsonpermalink

redirectpermalink

textpermalink

@sveltejs/kit/hookspermalink

sequencepermalink

@sveltejs/kit/nodepermalink

getRequestpermalink

setResponsepermalink

@sveltejs/kit/node/polyfillspermalink

installPolyfillspermalink

@sveltejs/kit/vitepermalink

sveltekitpermalink

`$lib/server`permalink