Reference

Types

Public typespermalink

The following types can be imported from @sveltejs/kit:

Actionpermalink

Shape of a form action method that is part of export const actions = {..} in +page.server.js. See form actions for more information.

ts
type Action<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	OutputData extends Record<string, any> | void = Record<
		string,
		any
	> | void,
	RouteId extends string | null = string | null
> = (
	event: RequestEvent<Params, RouteId>
) => MaybePromise<OutputData>;

ActionFailurepermalink

ts
interface ActionFailure<
	T extends Record<string, unknown> | undefined = undefined
> {…}

ts
status: number;

ts
data: T;

ts
[uniqueSymbol]: true;

ActionResultpermalink

When calling a form action via fetch, the response will be one of these shapes.

<form method="post" use:enhance={() => {
  return ({ result }) => {
		// result is of type ActionResult
  };
}}

ts
type ActionResult<
	Success extends
		| Record<string, unknown>
		| undefined = Record<string, any>,
	Failure extends
		| Record<string, unknown>
		| undefined = Record<string, any>
> =
	| { type: 'success'; status: number; data?: Success }
	| { type: 'failure'; status: number; data?: Failure }
	| { type: 'redirect'; status: number; location: string }
	| { type: 'error'; status?: number; error: any };

Actionspermalink

Shape of the export const actions = {..} object in +page.server.js. See form actions for more information.

ts
type Actions<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	OutputData extends Record<string, any> | void = Record<
		string,
		any
	> | void,
	RouteId extends string | null = string | null
> = Record<string, Action<Params, OutputData, RouteId>>;

Adapterpermalink

Adapters are responsible for taking the production build and turning it into something that can be deployed to a platform of your choosing.

ts
interface Adapter {…}

ts
name: string;

The name of the adapter, using for logging. Will typically correspond to the package name.

ts
adapt(builder: Builder): MaybePromise<void>;

builder An object provided by SvelteKit that contains methods for adapting the app

This function is called after SvelteKit has built your app.

AfterNavigatepermalink

The argument passed to afterNavigate callbacks.

ts
interface AfterNavigate extends Omit<Navigation, 'type'> {…}

ts
type: Exclude<NavigationType, 'leave'>;

The type of navigation:

enter: The app has hydrated
form: The user submitted a <form>
link: Navigation was triggered by a link click
goto: Navigation was triggered by a goto(...) call or a redirect
popstate: Navigation was triggered by back/forward navigation

ts
willUnload: false;

Since afterNavigate callbacks are called after a navigation completes, they will never be called with a navigation that unloads the page.

AwaitedActionspermalink

ts
type AwaitedActions<
	T extends Record<string, (...args: any) => any>
> = OptionalUnion<
	{
		[Key in keyof T]: UnpackValidationError<
			Awaited<ReturnType<T[Key]>>
		>;
	}[keyof T]
>;

BeforeNavigatepermalink

The argument passed to beforeNavigate callbacks.

ts
interface BeforeNavigate extends Navigation {…}

ts
cancel(): void;

Call this to prevent the navigation from starting.

Builderpermalink

This object is passed to the adapt function of adapters. It contains various methods and properties that are useful for adapting the app.

ts
interface Builder {…}

ts
log: Logger;

Print messages to the console. log.info and log.minor are silent unless Vite's logLevel is info.

ts
rimraf(dir: string): void;

Remove dir and all its contents.

ts
mkdirp(dir: string): void;

Create dir and any required parent directories.

ts
config: ValidatedConfig;

The fully resolved svelte.config.js.

ts
prerendered: Prerendered;

Information about prerendered pages and assets, if any.

ts
routes: RouteDefinition[];

An array of all routes (including prerendered)

ts
createEntries(fn: (route: RouteDefinition) => AdapterEntry): Promise<void>;

fn A function that groups a set of routes into an entry point
deprecated Use builder.routes instead

Create separate functions that map to one or more routes of your app.

ts
generateFallback(dest: string): Promise<void>;

Generate a fallback page for a static webserver to use when no route is matched. Useful for single-page apps.

ts
generateEnvModule(): void;

Generate a module exposing build-time environment variables as $env/dynamic/public.

ts
generateManifest(opts: { relativePath: string; routes?: RouteDefinition[] }): string;

opts a relative path to the base directory of the app and optionally in which format (esm or cjs) the manifest should be generated

Generate a server-side manifest to initialise the SvelteKit server with.

ts
getBuildDirectory(name: string): string;

name path to the file, relative to the build directory

Resolve a path to the name directory inside outDir, e.g. /path/to/.svelte-kit/my-adapter.

ts
getClientDirectory(): string;

Get the fully resolved path to the directory containing client-side assets, including the contents of your static directory.

ts
getServerDirectory(): string;

Get the fully resolved path to the directory containing server-side code.

ts
getAppPath(): string;

Get the application path including any configured base path, e.g. my-base-path/_app.

ts
writeClient(dest: string): string[];

dest the destination folder
returns an array of files written to dest

Write client assets to dest.

ts
writePrerendered(dest: string): string[];

dest the destination folder
returns an array of files written to dest

Write prerendered files to dest.

ts
writeServer(dest: string): string[];

dest the destination folder
returns an array of files written to dest

Write server-side code to dest.

ts
copy(
	from: string,
	to: string,
	opts?: {
		filter?(basename: string): boolean;
		replace?: Record<string, string>;
	}
): string[];

from the source file or directory
to the destination file or directory
opts.filter a function to determine whether a file or directory should be copied
opts.replace a map of strings to replace
returns an array of files that were copied

Copy a file or directory.

ts
compress(directory: string): Promise<void>;

directory The directory containing the files to be compressed

Compress files in directory with gzip and brotli, where appropriate. Generates .gz and .br files alongside the originals.

Configpermalink

ts
interface Config {…}

See the configuration reference for details.

Cookiespermalink

ts
interface Cookies {…}

ts
get(name: string, opts?: import('cookie').CookieParseOptions): string | undefined;

name the name of the cookie
opts the options, passed directly to cookie.parse. See documentation here

Gets a cookie that was previously set with cookies.set, or from the request headers.

ts
getAll(opts?: import('cookie').CookieParseOptions): Array<{ name: string; value: string }>;

opts the options, passed directly to cookie.parse. See documentation here

Gets all cookies that were previously set with cookies.set, or from the request headers.

ts
set(
	name: string,
	value: string,
	opts: import('cookie').CookieSerializeOptions & { path: string }
): void;

name the name of the cookie
value the cookie value
opts the options, passed directly to cookie.serialize. See documentation here

Sets a cookie. This will add a set-cookie header to the response, but also make the cookie available via cookies.get or cookies.getAll during the current request.

The httpOnly and secure options are true by default (except on http://localhost, where secure is false), and must be explicitly disabled if you want cookies to be readable by client-side JavaScript and/or transmitted over HTTP. The sameSite option defaults to lax.

You must specify a path for the cookie. In most cases you should explicitly set path: '/' to make the cookie available throughout your app. You can use relative paths, or set path: '' to make the cookie only available on the current path and its children

ts
delete(name: string, opts: import('cookie').CookieSerializeOptions & { path: string }): void;

name the name of the cookie
opts the options, passed directly to cookie.serialize. The path must match the path of the cookie you want to delete. See documentation here

Deletes a cookie by setting its value to an empty string and setting the expiry date in the past.

ts
serialize(
	name: string,
	value: string,
	opts: import('cookie').CookieSerializeOptions & { path: string }
): string;

name the name of the cookie
value the cookie value
opts the options, passed directly to cookie.serialize. See documentation here

Serialize a cookie name-value pair into a Set-Cookie header string, but don't apply it to the response.

Handlepermalink

The handle hook runs every time the SvelteKit server receives a request and determines the response. It receives an event object representing the request and a function called resolve, which renders the route and generates a Response. This allows you to modify response headers or bodies, or bypass SvelteKit entirely (for implementing routes programmatically, for example).

ts
type Handle = (input: {
	event: RequestEvent;
	resolve(
		event: RequestEvent,
		opts?: ResolveOptions
	): MaybePromise<Response>;
}) => MaybePromise<Response>;

HandleClientErrorpermalink

The client-side handleError hook runs when an unexpected error is thrown while navigating.

If an unexpected error is thrown during loading or the following render, this function will be called with the error and the event. Make sure that this function never throws an error.

ts
type HandleClientError = (input: {
	error: unknown;
	event: NavigationEvent;
	status: number;
	message: string;
}) => MaybePromise<void | App.Error>;

HandleFetchpermalink

The handleFetch hook allows you to modify (or replace) a fetch request that happens inside a load function that runs on the server (or during pre-rendering)

ts
type HandleFetch = (input: {
	event: RequestEvent;
	request: Request;
	fetch: typeof fetch;
}) => MaybePromise<Response>;

HandleServerErrorpermalink

The server-side handleError hook runs when an unexpected error is thrown while responding to a request.

If an unexpected error is thrown during loading or rendering, this function will be called with the error and the event. Make sure that this function never throws an error.

ts
type HandleServerError = (input: {
	error: unknown;
	event: RequestEvent;
	status: number;
	message: string;
}) => MaybePromise<void | App.Error>;

HttpErrorpermalink

The object returned by the error function.

ts
interface HttpError {…}

ts
status: number;

The HTTP status code, in the range 400-599.

ts
body: App.Error;

The content of the error.

KitConfigpermalink

ts
interface KitConfig {…}

See the configuration reference for details.

LessThanpermalink

ts
type LessThan<
	TNumber extends number,
	TArray extends any[] = []
> = TNumber extends TArray['length']
	? TArray[number]
	: LessThan<TNumber, [...TArray, TArray['length']]>;

Loadpermalink

The generic form of PageLoad and LayoutLoad. You should import those from ./$types (see generated types) rather than using Load directly.

ts
type Load<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	InputData extends Record<string, unknown> | null = Record<
		string,
		any
	> | null,
	ParentData extends Record<string, unknown> = Record<
		string,
		any
	>,
	OutputData extends Record<
		string,
		unknown
	> | void = Record<string, any> | void,
	RouteId extends string | null = string | null
> = (
	event: LoadEvent<Params, InputData, ParentData, RouteId>
) => MaybePromise<OutputData>;

LoadEventpermalink

The generic form of PageLoadEvent and LayoutLoadEvent. You should import those from ./$types (see generated types) rather than using LoadEvent directly.

ts
interface LoadEvent<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	Data extends Record<string, unknown> | null = Record<
		string,
		any
	> | null,
	ParentData extends Record<string, unknown> = Record<
		string,
		any
	>,
	RouteId extends string | null = string | null
> extends NavigationEvent<Params, RouteId> {…}

ts
fetch: typeof fetch;

fetch is equivalent to the native fetch web API, with a few additional features:

It can be used to make credentialed requests on the server, as it inherits the cookie and authorization headers for the page request.
It can make relative requests on the server (ordinarily, fetch requires a URL with an origin when used in a server context).
Internal requests (e.g. for +server.js routes) go directly to the handler function when running on the server, without the overhead of an HTTP call.
During server-side rendering, the response will be captured and inlined into the rendered HTML by hooking into the text and json methods of the Response object. Note that headers will not be serialized, unless explicitly included via filterSerializedResponseHeaders
During hydration, the response will be read from the HTML, guaranteeing consistency and preventing an additional network request.

You can learn more about making credentialed requests with cookies here

ts
data: Data;

Contains the data returned by the route's server load function (in +layout.server.js or +page.server.js), if any.

ts
setHeaders(headers: Record<string, string>): void;

If you need to set headers for the response, you can do so using the this method. This is useful if you want the page to be cached, for example:

src/routes/blog/+page.js

ts
export async function load({ fetch, setHeaders }) {
Binding element 'fetch' implicitly has an 'any' type.
Binding element 'setHeaders' implicitly has an 'any' type.7031
7031Binding element 'fetch' implicitly has an 'any' type.
Binding element 'setHeaders' implicitly has an 'any' type.	const url = `https://cms.example.com/articles.json`;
	const response = await fetch(url);

	setHeaders({
		age: response.headers.get('age'),
		'cache-control': response.headers.get('cache-control')
	});

	return response.json();
}

src/routes/blog/+page.ts

ts
export async function load({ fetch, setHeaders }) {
Binding element 'fetch' implicitly has an 'any' type.
Binding element 'setHeaders' implicitly has an 'any' type.7031
7031Binding element 'fetch' implicitly has an 'any' type.
Binding element 'setHeaders' implicitly has an 'any' type.	const url = `https://cms.example.com/articles.json`;
	const response = await fetch(url);

	setHeaders({
		age: response.headers.get('age'),
		'cache-control': response.headers.get('cache-control'),
	});

	return response.json();
}

Setting the same header multiple times (even in separate load functions) is an error — you can only set a given header once.

You cannot add a set-cookie header with setHeaders — use the cookies API in a server-only load function instead.

setHeaders has no effect when a load function runs in the browser.

ts
parent(): Promise<ParentData>;

await parent() returns data from parent +layout.js load functions. Implicitly, a missing +layout.js is treated as a ({ data }) => data function, meaning that it will return and forward data from parent +layout.server.js files.

Be careful not to introduce accidental waterfalls when using await parent(). If for example you only want to merge parent data into the returned output, call it after fetching your other data.

ts
depends(...deps: Array<`${string}:${string}`>): void;

This function declares that the load function has a dependency on one or more URLs or custom identifiers, which can subsequently be used with invalidate() to cause load to rerun.

Most of the time you won't need this, as fetch calls depends on your behalf — it's only necessary if you're using a custom API client that bypasses fetch.

URLs can be absolute or relative to the page being loaded, and must be encoded.

Custom identifiers have to be prefixed with one or more lowercase letters followed by a colon to conform to the URI specification.

The following example shows how to use depends to register a dependency on a custom identifier, which is invalidated after a button click, making the load function rerun.

src/routes/+page.js

ts
let count = 0;
export async function load({ depends }) {
Binding element 'depends' implicitly has an 'any' type.7031Binding element 'depends' implicitly has an 'any' type.	depends('increase:count');

	return { count: count++ };
}

src/routes/+page.ts

ts
let count = 0;
export async function load({ depends }) {
Binding element 'depends' implicitly has an 'any' type.7031Binding element 'depends' implicitly has an 'any' type.	depends('increase:count');

	return { count: count++ };
}

src/routes/+page.svelte

<script>
	import { invalidate } from '$app/navigation';

	export let data;

	const increase = async () => {
		await invalidate('increase:count');
	}
</script>

<p>{data.count}<p>
<button on:click={increase}>Increase Count</button>

ts
untrack<T>(fn: () => T): T;

Use this function to opt out of dependency tracking for everything that is synchronously called within the callback. Example:

src/routes/+page.server.js

ts
export async function load({ untrack, url }) {
Binding element 'untrack' implicitly has an 'any' type.
Binding element 'url' implicitly has an 'any' type.7031
7031Binding element 'untrack' implicitly has an 'any' type.
Binding element 'url' implicitly has an 'any' type.	// Untrack url.pathname so that path changes don't trigger a rerun
	if (untrack(() => url.pathname === '/')) {
		return { message: 'Welcome!' };
	}
}

src/routes/+page.server.ts

ts
export async function load({ untrack, url }) {
Binding element 'untrack' implicitly has an 'any' type.
Binding element 'url' implicitly has an 'any' type.7031
7031Binding element 'untrack' implicitly has an 'any' type.
Binding element 'url' implicitly has an 'any' type.	// Untrack url.pathname so that path changes don't trigger a rerun
	if (untrack(() => url.pathname === '/')) {
		return { message: 'Welcome!' };
	}
}

LoadPropertiespermalink

ts
type LoadProperties<
	input extends Record<string, any> | void
> = input extends void
	? undefined // needs to be undefined, because void will break intellisense
	: input extends Record<string, any>
		? input
		: unknown;

ts
interface Navigation {…}

ts
from: NavigationTarget | null;

Where navigation was triggered from

ts
to: NavigationTarget | null;

Where navigation is going to/has gone to

ts
type: Exclude<NavigationType, 'enter'>;

The type of navigation:

form: The user submitted a <form>
leave: The app is being left either because the tab is being closed or a navigation to a different document is occurring
link: Navigation was triggered by a link click
goto: Navigation was triggered by a goto(...) call or a redirect
popstate: Navigation was triggered by back/forward navigation

ts
willUnload: boolean;

Whether or not the navigation will result in the page being unloaded (i.e. not a client-side navigation)

ts
delta?: number;

In case of a history back/forward navigation, the number of steps to go back/forward

ts
complete: Promise<void>;

A promise that resolves once the navigation is complete, and rejects if the navigation fails or is aborted. In the case of a willUnload navigation, the promise will never resolve

NavigationEventpermalink

ts
interface NavigationEvent<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	RouteId extends string | null = string | null
> {…}

ts
params: Params;

The parameters of the current page - e.g. for a route like /blog/[slug], a { slug: string } object

ts
route: {…}

Info about the current route

ts
id: RouteId;

The ID of the current route - e.g. for src/routes/blog/[slug], it would be /blog/[slug]

ts
url: URL;

The URL of the current page

NavigationTargetpermalink

Information about the target of a specific navigation.

ts
interface NavigationTarget {…}

ts
params: Record<string, string> | null;

Parameters of the target page - e.g. for a route like /blog/[slug], a { slug: string } object. Is null if the target is not part of the SvelteKit app (could not be resolved to a route).

ts
route: { id: string | null };

Info about the target route

ts
url: URL;

The URL that is navigated to

NavigationTypepermalink

enter: The app has hydrated
form: The user submitted a <form> with a GET method
leave: The user is leaving the app by closing the tab or using the back/forward buttons to go to a different document
link: Navigation was triggered by a link click
goto: Navigation was triggered by a goto(...) call or a redirect
popstate: Navigation was triggered by back/forward navigation

ts
type NavigationType =
	| 'enter'
	| 'form'
	| 'leave'
	| 'link'
	| 'goto'
	| 'popstate';

NumericRangepermalink

ts
type NumericRange<
	TStart extends number,
	TEnd extends number
> = Exclude<TEnd | LessThan<TEnd>, LessThan<TStart>>;

OnNavigatepermalink

The argument passed to onNavigate callbacks.

ts
interface OnNavigate extends Navigation {…}

ts
type: Exclude<NavigationType, 'enter' | 'leave'>;

The type of navigation:

form: The user submitted a <form>
link: Navigation was triggered by a link click
goto: Navigation was triggered by a goto(...) call or a redirect
popstate: Navigation was triggered by back/forward navigation

ts
willUnload: false;

Since onNavigate callbacks are called immediately before a client-side navigation, they will never be called with a navigation that unloads the page.

Pagepermalink

The shape of the $page store

ts
interface Page<
	Params extends Record<string, string> = Record<
		string,
		string
	>,
	RouteId extends string | null = string | null
> {…}

ts
url: URL;

The URL of the current page

ts
params: Params;

The parameters of the current page - e.g. for a route like /blog/[slug], a { slug: string } object

ts
route: {…}

Info about the current route

ts
id: RouteId;

The ID of the current route - e.g. for src/routes/blog/[slug], it would be /blog/[slug]

ts
status: number;

Http status code of the current page

ts
error: App.Error | null;

The error object of the current page, if any. Filled from the handleError hooks.

ts
data: App.PageData & Record<string, any>;

The merged result of all data from all load functions on the current page. You can type a common denominator through App.PageData.

ts
state: App.PageState;

The page state, which can be manipulated using the pushState and replaceState functions from $app/navigation.

ts
form: any;

Filled only after a form submission. See form actions for more info.

ParamMatcherpermalink

The shape of a param matcher. See matching for more info.

ts
type ParamMatcher = (param: string) => boolean;

PrerenderOptionpermalink

ts
type PrerenderOption = boolean | 'auto';

Redirectpermalink

The object returned by the redirect function

ts
interface Redirect {…}

ts
status: 300 | 301 | 302 | 303 | 304 | 305 | 306 | 307 | 308;

The HTTP status code, in the range 300-308.

ts
location: string;

The location to redirect to.

RequestEventpermalink

ts
interface RequestEvent<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	RouteId extends string | null = string | null
> {…}

ts
cookies: Cookies;

Get or set cookies related to the current request

ts
fetch: typeof fetch;

fetch is equivalent to the native fetch web API, with a few additional features:

It can be used to make credentialed requests on the server, as it inherits the cookie and authorization headers for the page request.
It can make relative requests on the server (ordinarily, fetch requires a URL with an origin when used in a server context).
Internal requests (e.g. for +server.js routes) go directly to the handler function when running on the server, without the overhead of an HTTP call.
During server-side rendering, the response will be captured and inlined into the rendered HTML by hooking into the text and json methods of the Response object. Note that headers will not be serialized, unless explicitly included via filterSerializedResponseHeaders
During hydration, the response will be read from the HTML, guaranteeing consistency and preventing an additional network request.

You can learn more about making credentialed requests with cookies here

ts
getClientAddress(): string;

The client's IP address, set by the adapter.

ts
locals: App.Locals;

Contains custom data that was added to the request within the handle hook.

ts
params: Params;

The parameters of the current route - e.g. for a route like /blog/[slug], a { slug: string } object

ts
platform: Readonly<App.Platform> | undefined;

Additional data made available through the adapter.

ts
request: Request;

The original request object

ts
route: {…}

Info about the current route

ts
id: RouteId;

The ID of the current route - e.g. for src/routes/blog/[slug], it would be /blog/[slug]

ts
setHeaders(headers: Record<string, string>): void;

If you need to set headers for the response, you can do so using the this method. This is useful if you want the page to be cached, for example:

src/routes/blog/+page.js

ts
export async function load({ fetch, setHeaders }) {
Binding element 'fetch' implicitly has an 'any' type.
Binding element 'setHeaders' implicitly has an 'any' type.7031
7031Binding element 'fetch' implicitly has an 'any' type.
Binding element 'setHeaders' implicitly has an 'any' type.	const url = `https://cms.example.com/articles.json`;
	const response = await fetch(url);

	setHeaders({
		age: response.headers.get('age'),
		'cache-control': response.headers.get('cache-control')
	});

	return response.json();
}

src/routes/blog/+page.ts

ts
export async function load({ fetch, setHeaders }) {
Binding element 'fetch' implicitly has an 'any' type.
Binding element 'setHeaders' implicitly has an 'any' type.7031
7031Binding element 'fetch' implicitly has an 'any' type.
Binding element 'setHeaders' implicitly has an 'any' type.	const url = `https://cms.example.com/articles.json`;
	const response = await fetch(url);

	setHeaders({
		age: response.headers.get('age'),
		'cache-control': response.headers.get('cache-control'),
	});

	return response.json();
}

Setting the same header multiple times (even in separate load functions) is an error — you can only set a given header once.

You cannot add a set-cookie header with setHeaders — use the cookies API instead.

ts
url: URL;

The requested URL.

ts
isDataRequest: boolean;

true if the request comes from the client asking for +page/layout.server.js data. The url property will be stripped of the internal information related to the data request in this case. Use this property instead if the distinction is important to you.

ts
isSubRequest: boolean;

true for +server.js calls coming from SvelteKit without the overhead of actually making an HTTP request. This happens when you make same-origin fetch requests on the server.

RequestHandlerpermalink

A (event: RequestEvent) => Response function exported from a +server.js file that corresponds to an HTTP verb (GET, PUT, PATCH, etc) and handles requests with that method.

It receives Params as the first generic argument, which you can skip by using generated types instead.

ts
type RequestHandler<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	RouteId extends string | null = string | null
> = (
	event: RequestEvent<Params, RouteId>
) => MaybePromise<Response>;

Reroutepermalink

The reroute hook allows you to modify the URL before it is used to determine which route to render.

ts
type Reroute = (event: { url: URL }) => void | string;

ResolveOptionspermalink

ts
interface ResolveOptions {…}

ts
transformPageChunk?(input: { html: string; done: boolean }): MaybePromise<string | undefined>;

input the html chunk and the info if this is the last chunk

Applies custom transforms to HTML. If done is true, it's the final chunk. Chunks are not guaranteed to be well-formed HTML (they could include an element's opening tag but not its closing tag, for example) but they will always be split at sensible boundaries such as %sveltekit.head% or layout/page components.

ts
filterSerializedResponseHeaders?(name: string, value: string): boolean;

name header name
value header value

Determines which headers should be included in serialized responses when a load function loads a resource with fetch. By default, none will be included.

ts
preload?(input: { type: 'font' | 'css' | 'js' | 'asset'; path: string }): boolean;

input the type of the file and its path

Determines what should be added to the <head> tag to preload it. By default, js and css files will be preloaded.

RouteDefinitionpermalink

ts
interface RouteDefinition<Config = any> {…}

ts
id: string;

ts
api: {
	methods: Array<HttpMethod | '*'>;
};

ts
page: {
	methods: Array<Extract<HttpMethod, 'GET' | 'POST'>>;
};

ts
pattern: RegExp;

ts
prerender: PrerenderOption;

ts
segments: RouteSegment[];

ts
methods: Array<HttpMethod | '*'>;

ts
config: Config;

SSRManifestpermalink

ts
interface SSRManifest {…}

ts
appDir: string;

ts
appPath: string;

ts
assets: Set<string>;

ts
mimeTypes: Record<string, string>;

ts
_: {
	client: NonNullable<BuildData['client']>;
	files: Record<string, [length: number, type: string]>;
	nodes: SSRNodeLoader[];
	routes: SSRRoute[];
	matchers(): Promise<Record<string, ParamMatcher>>;
};

private fields

Serverpermalink

ts
class Server {…}

ts
constructor(manifest: SSRManifest);

ts
init(options: ServerInitOptions): Promise<void>;

ts
respond(request: Request, options: RequestOptions): Promise<Response>;

ServerInitOptionspermalink

ts
interface ServerInitOptions {…}

ts
env: Record<string, string>;

ts
readAsset?: (file: string) => ReadableStream;

ServerLoadpermalink

The generic form of PageServerLoad and LayoutServerLoad. You should import those from ./$types (see generated types) rather than using ServerLoad directly.

ts
type ServerLoad<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	ParentData extends Record<string, any> = Record<
		string,
		any
	>,
	OutputData extends Record<string, any> | void = Record<
		string,
		any
	> | void,
	RouteId extends string | null = string | null
> = (
	event: ServerLoadEvent<Params, ParentData, RouteId>
) => MaybePromise<OutputData>;

ServerLoadEventpermalink

ts
interface ServerLoadEvent<
	Params extends Partial<Record<string, string>> = Partial<
		Record<string, string>
	>,
	ParentData extends Record<string, any> = Record<
		string,
		any
	>,
	RouteId extends string | null = string | null
> extends RequestEvent<Params, RouteId> {…}

ts
parent(): Promise<ParentData>;

await parent() returns data from parent +layout.server.js load functions.

Be careful not to introduce accidental waterfalls when using await parent(). If for example you only want to merge parent data into the returned output, call it after fetching your other data.

ts
depends(...deps: string[]): void;

This function declares that the load function has a dependency on one or more URLs or custom identifiers, which can subsequently be used with invalidate() to cause load to rerun.

Most of the time you won't need this, as fetch calls depends on your behalf — it's only necessary if you're using a custom API client that bypasses fetch.

URLs can be absolute or relative to the page being loaded, and must be encoded.

Custom identifiers have to be prefixed with one or more lowercase letters followed by a colon to conform to the URI specification.

The following example shows how to use depends to register a dependency on a custom identifier, which is invalidated after a button click, making the load function rerun.

src/routes/+page.js

ts
let count = 0;
export async function load({ depends }) {
Binding element 'depends' implicitly has an 'any' type.7031Binding element 'depends' implicitly has an 'any' type.	depends('increase:count');

	return { count: count++ };
}

src/routes/+page.ts

ts
let count = 0;
export async function load({ depends }) {
Binding element 'depends' implicitly has an 'any' type.7031Binding element 'depends' implicitly has an 'any' type.	depends('increase:count');

	return { count: count++ };
}

src/routes/+page.svelte

<script>
	import { invalidate } from '$app/navigation';

	export let data;

	const increase = async () => {
		await invalidate('increase:count');
	}
</script>

<p>{data.count}<p>
<button on:click={increase}>Increase Count</button>

ts
untrack<T>(fn: () => T): T;

Use this function to opt out of dependency tracking for everything that is synchronously called within the callback. Example:

src/routes/+page.js

ts
export async function load({ untrack, url }) {
Binding element 'untrack' implicitly has an 'any' type.
Binding element 'url' implicitly has an 'any' type.7031
7031Binding element 'untrack' implicitly has an 'any' type.
Binding element 'url' implicitly has an 'any' type.	// Untrack url.pathname so that path changes don't trigger a rerun
	if (untrack(() => url.pathname === '/')) {
		return { message: 'Welcome!' };
	}
}

src/routes/+page.ts

ts
export async function load({ untrack, url }) {
Binding element 'untrack' implicitly has an 'any' type.
Binding element 'url' implicitly has an 'any' type.7031
7031Binding element 'untrack' implicitly has an 'any' type.
Binding element 'url' implicitly has an 'any' type.	// Untrack url.pathname so that path changes don't trigger a rerun
	if (untrack(() => url.pathname === '/')) {
		return { message: 'Welcome!' };
	}
}

Snapshotpermalink

The type of export const snapshot exported from a page or layout component.

ts
interface Snapshot<T = any> {…}

ts
capture: () => T;

ts
restore: (snapshot: T) => void;

SubmitFunctionpermalink

ts
type SubmitFunction<
	Success extends
		| Record<string, unknown>
		| undefined = Record<string, any>,
	Failure extends
		| Record<string, unknown>
		| undefined = Record<string, any>
> = (input: {
	action: URL;
	formData: FormData;
	formElement: HTMLFormElement;
	controller: AbortController;
	submitter: HTMLElement | null;
	cancel(): void;
}) => MaybePromise<
	| void
	| ((opts: {
			formData: FormData;
			formElement: HTMLFormElement;
			action: URL;
			result: ActionResult<Success, Failure>;
			/**
			 * Call this to get the default behavior of a form submission response.
			 * @param options Set `reset: false` if you don't want the `<form>` values to be reset after a successful submission.
			 * @param invalidateAll Set `invalidateAll: false` if you don't want the action to call `invalidateAll` after submission.
			 */
			update(options?: {
				reset?: boolean;
				invalidateAll?: boolean;
			}): Promise<void>;
	  }) => void)
>;

Private typespermalink

The following are referenced by the public types documented above, but cannot be imported directly:

AdapterEntrypermalink

ts
interface AdapterEntry {…}

ts
id: string;

A string that uniquely identifies an HTTP service (e.g. serverless function) and is used for deduplication. For example, /foo/a-[b] and /foo/[c] are different routes, but would both be represented in a Netlify _redirects file as /foo/:param, so they share an ID

ts
filter(route: RouteDefinition): boolean;

A function that compares the candidate route with the current route to determine if it should be grouped with the current route.

Use cases:

Fallback pages: /foo/[c] is a fallback for /foo/a-[b], and /[...catchall] is a fallback for all routes
Grouping routes that share a common config: /foo should be deployed to the edge, /bar and /baz should be deployed to a serverless function

ts
complete(entry: { generateManifest(opts: { relativePath: string }): string }): MaybePromise<void>;

A function that is invoked once the entry has been created. This is where you should write the function to the filesystem and generate redirect manifests.

Csppermalink

ts
namespace Csp {
	type ActionSource = 'strict-dynamic' | 'report-sample';
	type BaseSource =
		| 'self'
		| 'unsafe-eval'
		| 'unsafe-hashes'
		| 'unsafe-inline'
		| 'wasm-unsafe-eval'
		| 'none';
	type CryptoSource = `${
		| 'nonce'
		| 'sha256'
		| 'sha384'
		| 'sha512'}-${string}`;
	type FrameSource =
		| HostSource
		| SchemeSource
		| 'self'
		| 'none';
	type HostNameScheme = `${string}.${string}` | 'localhost';
	type HostSource =
		`${HostProtocolSchemes}${HostNameScheme}${PortScheme}`;
	type HostProtocolSchemes = `${string}://` | '';
	type HttpDelineator = '/' | '?' | '#' | '\\';
	type PortScheme = `:${number}` | '' | ':*';
	type SchemeSource =
		| 'http:'
		| 'https:'
		| 'data:'
		| 'mediastream:'
		| 'blob:'
		| 'filesystem:';
	type Source =
		| HostSource
		| SchemeSource
		| CryptoSource
		| BaseSource;
	type Sources = Source[];
	type UriPath = `${HttpDelineator}${string}`;
}

CspDirectivespermalink

ts
interface CspDirectives {…}

ts
'child-src'?: Csp.Sources;

ts
'default-src'?: Array<Csp.Source | Csp.ActionSource>;

ts
'frame-src'?: Csp.Sources;

ts
'worker-src'?: Csp.Sources;

ts
'connect-src'?: Csp.Sources;

ts
'font-src'?: Csp.Sources;

ts
'img-src'?: Csp.Sources;

ts
'manifest-src'?: Csp.Sources;

ts
'media-src'?: Csp.Sources;

ts
'object-src'?: Csp.Sources;

ts
'prefetch-src'?: Csp.Sources;

ts
'script-src'?: Array<Csp.Source | Csp.ActionSource>;

ts
'script-src-elem'?: Csp.Sources;

ts
'script-src-attr'?: Csp.Sources;

ts
'style-src'?: Array<Csp.Source | Csp.ActionSource>;

ts
'style-src-elem'?: Csp.Sources;

ts
'style-src-attr'?: Csp.Sources;

ts
'base-uri'?: Array<Csp.Source | Csp.ActionSource>;

ts
sandbox?: Array<
| 'allow-downloads-without-user-activation'
| 'allow-forms'
| 'allow-modals'
| 'allow-orientation-lock'
| 'allow-pointer-lock'
| 'allow-popups'
| 'allow-popups-to-escape-sandbox'
| 'allow-presentation'
| 'allow-same-origin'
| 'allow-scripts'
| 'allow-storage-access-by-user-activation'
| 'allow-top-navigation'
| 'allow-top-navigation-by-user-activation'
>;

ts
'form-action'?: Array<Csp.Source | Csp.ActionSource>;

ts
'frame-ancestors'?: Array<Csp.HostSource | Csp.SchemeSource | Csp.FrameSource>;

ts
'navigate-to'?: Array<Csp.Source | Csp.ActionSource>;

ts
'report-uri'?: Csp.UriPath[];

ts
'report-to'?: string[];

ts
'require-trusted-types-for'?: Array<'script'>;

ts
'trusted-types'?: Array<'none' | 'allow-duplicates' | '*' | string>;

ts
'upgrade-insecure-requests'?: boolean;

ts
'require-sri-for'?: Array<'script' | 'style' | 'script style'>;

deprecated undefined

ts
'block-all-mixed-content'?: boolean;

deprecated undefined

ts
'plugin-types'?: Array<`${string}/${string}` | 'none'>;

deprecated undefined

ts
referrer?: Array<
| 'no-referrer'
| 'no-referrer-when-downgrade'
| 'origin'
| 'origin-when-cross-origin'
| 'same-origin'
| 'strict-origin'
| 'strict-origin-when-cross-origin'
| 'unsafe-url'
| 'none'
>;

deprecated undefined

HttpMethodpermalink

ts
type HttpMethod =
	| 'GET'
	| 'HEAD'
	| 'POST'
	| 'PUT'
	| 'DELETE'
	| 'PATCH'
	| 'OPTIONS';

Loggerpermalink

ts
interface Logger {…}

ts
(msg: string): void;

ts
success(msg: string): void;

ts
error(msg: string): void;

ts
warn(msg: string): void;

ts
minor(msg: string): void;

ts
info(msg: string): void;

MaybePromisepermalink

ts
type MaybePromise<T> = T | Promise<T>;

PrerenderEntryGeneratorMismatchHandlerpermalink

ts
interface PrerenderEntryGeneratorMismatchHandler {…}

ts
(details: { generatedFromId: string; entry: string; matchedId: string; message: string }): void;

PrerenderEntryGeneratorMismatchHandlerValuepermalink

ts
type PrerenderEntryGeneratorMismatchHandlerValue =
	| 'fail'
	| 'warn'
	| 'ignore'
	| PrerenderEntryGeneratorMismatchHandler;

PrerenderHttpErrorHandlerpermalink

ts
interface PrerenderHttpErrorHandler {…}

ts
(details: {
status: number;
path: string;
referrer: string | null;
referenceType: 'linked' | 'fetched';
message: string;
}): void;

PrerenderHttpErrorHandlerValuepermalink

ts
type PrerenderHttpErrorHandlerValue =
	| 'fail'
	| 'warn'
	| 'ignore'
	| PrerenderHttpErrorHandler;

PrerenderMappermalink

ts
type PrerenderMap = Map<string, PrerenderOption>;

PrerenderMissingIdHandlerpermalink

ts
interface PrerenderMissingIdHandler {…}

ts
(details: { path: string; id: string; referrers: string[]; message: string }): void;

PrerenderMissingIdHandlerValuepermalink

ts
type PrerenderMissingIdHandlerValue =
	| 'fail'
	| 'warn'
	| 'ignore'
	| PrerenderMissingIdHandler;

PrerenderOptionpermalink

ts
type PrerenderOption = boolean | 'auto';

Prerenderedpermalink

ts
interface Prerendered {…}

ts
pages: Map<
string,
{
	/** The location of the .html file relative to the output directory */
	file: string;
}
>;

A map of path to { file } objects, where a path like /foo corresponds to foo.html and a path like /bar/ corresponds to bar/index.html.

ts
assets: Map<
string,
{
	/** The MIME type of the asset */
	type: string;
}
>;

A map of path to { type } objects.

ts
redirects: Map<
string,
{
	status: number;
	location: string;
}
>;

A map of redirects encountered during prerendering.

ts
paths: string[];

An array of prerendered paths (without trailing slashes, regardless of the trailingSlash config)

RequestOptionspermalink

ts
interface RequestOptions {…}

ts
getClientAddress(): string;

ts
platform?: App.Platform;

RouteSegmentpermalink

ts
interface RouteSegment {…}

ts
content: string;

ts
dynamic: boolean;

ts
rest: boolean;

TrailingSlashpermalink

ts
type TrailingSlash = 'never' | 'always' | 'ignore';

Generated typespermalink

The RequestHandler and Load types both accept a Params argument allowing you to type the params object. For example this endpoint expects foo, bar and baz params:

src/routes/[foo]/[bar]/[baz]/+page.server.js

ts
/** @type {import('@sveltejs/kit').RequestHandler<{
	foo: string;
	bar: string;
	baz: string
  }>} */
export async function GET({ params }) {
A function whose declared type is neither 'void' nor 'any' must return a value.2355A function whose declared type is neither 'void' nor 'any' must return a value.	// ...
}

src/routes/[foo]/[bar]/[baz]/+page.server.ts

ts
export const GET: import('@sveltejs/kit').RequestHandler<{
Type '({ params }: RequestEvent<{ foo: string; bar: string; baz: string; }, string | null>) => Promise<void>' is not assignable to type 'RequestHandler<{ foo: string; bar: string; baz: string; }, string | null>'.
  Type 'Promise<void>' is not assignable to type 'MaybePromise<Response>'.
    Type 'Promise<void>' is not assignable to type 'Promise<Response>'.
      Type 'void' is not assignable to type 'Response'.2322Type '({ params }: RequestEvent<{ foo: string; bar: string; baz: string; }, string | null>) => Promise<void>' is not assignable to type 'RequestHandler<{ foo: string; bar: string; baz: string; }, string | null>'.
  Type 'Promise<void>' is not assignable to type 'MaybePromise<Response>'.
    Type 'Promise<void>' is not assignable to type 'Promise<Response>'.
      Type 'void' is not assignable to type 'Response'.	foo: string;
	bar: string;
	baz: string;
}> = async ({ params }) => {
	// ...
};

Needless to say, this is cumbersome to write out, and less portable (if you were to rename the [foo] directory to [qux], the type would no longer reflect reality).

To solve this problem, SvelteKit generates .d.ts files for each of your endpoints and pages:

.svelte-kit/types/src/routes/[foo]/[bar]/[baz]/$types.d.ts

ts
import type * as Kit from '@sveltejs/kit';

type RouteParams = {
	foo: string;
	bar: string;
	baz: string;
}

export type PageServerLoad = Kit.ServerLoad<RouteParams>;
export type PageLoad = Kit.Load<RouteParams>;

These files can be imported into your endpoints and pages as siblings, thanks to the rootDirs option in your TypeScript configuration:

src/routes/[foo]/[bar]/[baz]/+page.server.js

ts
/** @type {import('./$types').PageServerLoad} */
export async function GET({ params }) {
	// ...
}

src/routes/[foo]/[bar]/[baz]/+page.server.ts

ts
import type { PageServerLoad } from './$types';

export const GET: PageServerLoad = async ({ params }) => {
	// ...
};

src/routes/[foo]/[bar]/[baz]/+page.js

ts
/** @type {import('./$types').PageLoad} */
export async function load({ params, fetch }) {
	// ...
}

src/routes/[foo]/[bar]/[baz]/+page.ts

ts
import type { PageLoad } from './$types';

export const load: PageLoad = async ({ params, fetch }) => {
	// ...
};

For this to work, your own tsconfig.json or jsconfig.json should extend from the generated .svelte-kit/tsconfig.json (where .svelte-kit is your outDir):

{ "extends": "./.svelte-kit/tsconfig.json" }

Default tsconfig.jsonpermalink

The generated .svelte-kit/tsconfig.json file contains a mixture of options. Some are generated programmatically based on your project configuration, and should generally not be overridden without good reason:

.svelte-kit/tsconfig.json

ts
{
	"compilerOptions": {
		"baseUrl": "..",
		"paths": {
			"$lib": "src/lib",
			"$lib/*": "src/lib/*"
		},
		"rootDirs": ["..", "./types"]
	},
	"include": ["../src/**/*.js", "../src/**/*.ts", "../src/**/*.svelte"],
	"exclude": ["../node_modules/**", "./**"]
}

Others are required for SvelteKit to work properly, and should also be left untouched unless you know what you're doing:

.svelte-kit/tsconfig.json

ts
{
	"compilerOptions": {
		// this ensures that types are explicitly
		// imported with `import type`, which is
		// necessary as svelte-preprocess cannot
		// otherwise compile components correctly
		"importsNotUsedAsValues": "error",

		// Vite compiles one TypeScript module
		// at a time, rather than compiling
		// the entire module graph
		"isolatedModules": true,

		// TypeScript cannot 'see' when you
		// use an imported value in your
		// markup, so we need this
		"preserveValueImports": true,

		// This ensures both `vite build`
		// and `svelte-package` work correctly
		"lib": ["esnext", "DOM", "DOM.Iterable"],
		"moduleResolution": "node",
		"module": "esnext",
		"target": "esnext"
	}
}

Apppermalink

Errorpermalink

Defines the common shape of expected and unexpected errors. Expected errors are thrown using the error function. Unexpected errors are handled by the handleError hooks which should return this shape.

ts
interface Error {…}

ts
message: string;

Localspermalink

The interface that defines event.locals, which can be accessed in hooks (handle, and handleError), server-only load functions, and +server.js files.

ts
interface Locals {}

PageDatapermalink

Defines the common shape of the $page.data store - that is, the data that is shared between all pages. The Load and ServerLoad functions in ./$types will be narrowed accordingly. Use optional properties for data that is only present on specific pages. Do not add an index signature ([key: string]: any).

ts
interface PageData {}

PageStatepermalink

The shape of the $page.state object, which can be manipulated using the pushState and replaceState functions from $app/navigation.

ts
interface PageState {}

Platformpermalink

If your adapter provides platform-specific context via event.platform, you can specify it here.

ts
interface Platform {}

previous Modules

next Frequently asked questions

Types

Public typespermalink

Actionpermalink

ActionFailurepermalink

ActionResultpermalink

Actionspermalink

Adapterpermalink

AfterNavigatepermalink

AwaitedActionspermalink

BeforeNavigatepermalink

Builderpermalink

Configpermalink

Cookiespermalink

Handlepermalink

HandleClientErrorpermalink

HandleFetchpermalink

HandleServerErrorpermalink

HttpErrorpermalink

KitConfigpermalink

LessThanpermalink

Loadpermalink

LoadEventpermalink

LoadPropertiespermalink

Navigationpermalink

NavigationEventpermalink

NavigationTargetpermalink

NavigationTypepermalink

NumericRangepermalink

OnNavigatepermalink

Pagepermalink

ParamMatcherpermalink

PrerenderOptionpermalink

Redirectpermalink

RequestEventpermalink

RequestHandlerpermalink

Reroutepermalink

ResolveOptionspermalink

RouteDefinitionpermalink

SSRManifestpermalink

Serverpermalink

ServerInitOptionspermalink

ServerLoadpermalink

ServerLoadEventpermalink

Snapshotpermalink

SubmitFunctionpermalink

Private typespermalink

AdapterEntrypermalink

Csppermalink

CspDirectivespermalink

HttpMethodpermalink

Loggerpermalink

MaybePromisepermalink

PrerenderEntryGeneratorMismatchHandlerpermalink

PrerenderEntryGeneratorMismatchHandlerValuepermalink

PrerenderHttpErrorHandlerpermalink

PrerenderHttpErrorHandlerValuepermalink

PrerenderMappermalink

PrerenderMissingIdHandlerpermalink

PrerenderMissingIdHandlerValuepermalink

PrerenderOptionpermalink

Prerenderedpermalink

RequestOptionspermalink

RouteSegmentpermalink

TrailingSlashpermalink

Generated typespermalink

Default tsconfig.jsonpermalink

Apppermalink

Errorpermalink

Localspermalink

PageDatapermalink

PageStatepermalink

Platformpermalink