@auth/sveltekit

SvelteKit Auth is the official SvelteKit integration for Auth.js. It provides a simple way to add authentication to your SvelteKit app in a few lines of code.

Installation

npm install @auth/sveltekit

pnpm add @auth/sveltekit

yarn add @auth/sveltekit

bun add @auth/sveltekit

Usage

 
import { SvelteKitAuth } from "@auth/sveltekit"
import GitHub from "@auth/sveltekit/providers/github"
 
export const { handle, signIn, signOut } = SvelteKitAuth({
  providers: [GitHub],
})

Lazy initialization

@auth/sveltekit supports lazy initialization where you can read the event object to lazily set the configuration. This is especially useful when you have to get the environment variables from event.platform for platforms like Cloudflare Workers.

import { SvelteKitAuth } from "@auth/sveltekit"
import GitHub from "@auth/sveltekit/providers/github"
 
export const { handle, signIn, signOut } = SvelteKitAuth(async (event) => {
  const authOptions = {
    providers: [
      GitHub({
        clientId: event.platform.env.AUTH_GITHUB_ID,
        clientSecret: event.platform.env.AUTH_GITHUB_SECRET
      })
    ],
    secret: event.platform.env.AUTH_SECRET,
    trustHost: true
  }
  return authOptions
})

Re-export the handle in src/hooks.server.ts:

export { handle } from "./auth"

Remember to set the AUTH_SECRET environment variable. This should be a minimum of 32 characters, random string. On UNIX systems you can use openssl rand -hex 32 or check out https://generate-secret.vercel.app/32.

When deploying your app outside Vercel, set the AUTH_TRUST_HOST variable to true for other hosting providers like Cloudflare Pages or Netlify.

The callback URL used by the providers must be set to the following, unless you override SvelteKitAuthConfig.basePath:

[origin]/auth/callback/[provider]

Signing in and Signing out

Server-side

<SignIn /> and <SignOut /> are components that @auth/sveltekit provides out of the box - they handle the sign-in/signout flow, and can be used as-is as a starting point or customized for your own components. This is an example of how to use the SignIn and SignOut components to login and logout using SvelteKit’s server-side form actions. You will need two things to make this work:

1. Using the components in your SvelteKit app’s frontend
2. Add the required page.server.ts at /signin (for SignIn) and /signout (for SignOut) to handle the form actions

<script>
  import { SignIn, SignOut } from "@auth/sveltekit/components"
  import { page } from "$app/stores"
</script>
 
<h1>SvelteKit Auth Example</h1>
<div>
  {#if $page.data.session}
    {#if $page.data.session.user?.image}
      <img
        src={$page.data.session.user.image}
        class="avatar"
        alt="User Avatar"
      />
    {/if}
    <span class="signedInText">
      <small>Signed in as</small><br />
      <strong>{$page.data.session.user?.name ?? "User"}</strong>
    </span>
    <SignOut>
      <div slot="submitButton" class="buttonPrimary">Sign out</div>
    </SignOut>
  {:else}
    <span class="notSignedInText">You are not signed in</span>
    <SignIn>
      <div slot="submitButton" class="buttonPrimary">Sign in</div>
    </SignIn>
    <SignIn provider="facebook"/>
  {/if}
</div>

To set up the form actions, we need to define the files in src/routes:

import { signIn } from "../../auth"
import type { Actions } from "./$types"
export const actions: Actions = { default: signIn }

import { signOut } from "../../auth"
import type { Actions } from "./$types"
export const actions: Actions = { default: signOut }

These routes are customizeable with the signInPage and signOutPage props on the respective comopnents.

Client-Side

We also export two methods from @auth/sveltekit/client in order to do client-side sign-in and sign-out actions.

import { signIn, signOut } from "@auth/sveltekit/client"
 
<nav>
  <p>
    These actions are all using the methods exported from
    <code>@auth/sveltekit/client</code>
  </p>
  <div class="actions">
    <div class="wrapper-form">
      <button on:click={() => signIn("github")}>Sign In with GitHub</button>
    </div>
    <div class="wrapper-form">
      <button on:click={() => signIn("discord")}>Sign In with Discord</button>
    </div>
    <div class="wrapper-form">
      <div class="input-wrapper">
        <label for="password">Password</label>
        <input
          bind:value={password}
          type="password"
          id="password"
          name="password"
          required
        />
      </div>
      <button on:click={() => signIn("credentials", { password })}>
        Sign In with Credentials
      </button>
      <button on:click={() => signOut()})}>
        Sign Out
      </button>
    </div>
  </div>
</nav>

Managing the session

The above example checks for a session available in $page.data.session, however that needs to be set by us somewhere. If you want this data to be available to all your routes you can add this to src/routes/+layout.server.ts. The following code sets the session data in the $page store to be available to all routes.

import type { LayoutServerLoad } from './$types';
 
export const load: LayoutServerLoad = async (event) => {
  return {
    session: await event.locals.auth()
  };
};

What you return in the function LayoutServerLoad will be available inside the $page store, in the data property: $page.data. In this case we return an object with the ‘session’ property which is what we are accessing in the other code paths.

Handling authorization

In SvelteKit there are a few ways you could protect routes from unauthenticated users.

Per component

The simplest case is protecting a single page, in which case you should put the logic in the +page.server.ts file. Notice in this case that you could also await event.parent and grab the session from there, however this implementation works even if you haven’t done the above in your root +layout.server.ts

import { redirect } from '@sveltejs/kit';
import type { PageServerLoad } from './$types';
 
export const load: PageServerLoad = async (event) => {
  const session = await event.locals.auth();
  if (!session?.user) throw redirect(303, '/auth');
  return {};
};

You should NOT put authorization logic in a +layout.server.ts as the logic is not guaranteed to propagate to leafs in the tree. Prefer to manually protect each route through the +page.server.ts file to avoid mistakes. It is possible to force the layout file to run the load function on all routes, however that relies certain behaviours that can change and are not easily checked. For more information about these caveats make sure to read this issue in the SvelteKit repository: https://github.com/sveltejs/kit/issues/6315

Per path

Another method that’s possible for handling authorization is by restricting certain URIs from being available. For many projects this is better because:

• This automatically protects actions and api routes in those URIs
• No code duplication between components
• Very easy to modify

The way to handle authorization through the URI is to override your handle hook. The handle hook, returned from SvelteKitAuth in your src/auth.ts, is a function that is designed to receive ALL requests sent to your SvelteKit webapp. You should export it from src/auth.ts and import it in your src/hooks.server.ts. To use multiple handles in your hooks.server.ts, we can use SvelteKit’s sequence to execute all of them in series.

import { SvelteKitAuth } from '@auth/sveltekit';
import GitHub from '@auth/sveltekit/providers/github';
 
export const { handle, signIn, signOut } = SvelteKitAuth({
  providers: [GitHub]
}),

import { redirect, type Handle } from '@sveltejs/kit';
import { handle as authenticationHandle } from './auth';
import { sequence } from '@sveltejs/kit/hooks';
 
async function authorizationHandle({ event, resolve }) {
  // Protect any routes under /authenticated
  if (event.url.pathname.startsWith('/authenticated')) {
    const session = await event.locals.auth();
    if (!session) {
      // Redirect to the signin page
      throw redirect(303, '/auth/signin');
    }
  }
 
  // If the request is still here, just proceed as normally
  return resolve(event);
}
 
// First handle authentication, then authorization
// Each function acts as a middleware, receiving the request handle
// And returning a handle which gets passed to the next function
export const handle: Handle = sequence(authenticationHandle, authorizationHandle)

Now any routes under /authenticated will be transparently protected by the handle hook. You may add more middleware-like functions to the sequence and also implement more complex authorization business logic inside this file. This can also be used along with the component-based approach in case you need a specific page to be protected and doing it by URI could be faulty.

Notes

• If you build your SvelteKit application with prerender enabled, pages which have an anchor tag to the default signin page (i.e. <a href="/auth/signin" ...) will have trouble building. Please use the builtin functions or components to sign in or out instead.

SvelteKitAuthConfig

Re-exports SvelteKitAuthConfig

AuthError

Base error class for all Auth.js errors. It’s optimized to be printed in the server logs in a nicely formatted way via the logger.error option.

Extends

• Error

Constructors

new AuthError(message, errorOptions)

new AuthError(message?, errorOptions?): AuthError

Parameters

Returns

AuthError

Overrides

Error.constructor

Properties

cause?

optional cause: Record<string, unknown> & {
  err: Error;
};

Type declaration

err?

optional err: Error;

Overrides

Error.cause

message

message: string;

Inherited from

Error.message

name

name: string;

Inherited from

Error.name

stack?

optional stack: string;

Inherited from

Error.stack

type

type: ErrorType;

The error type. Used to identify the error in the logs.

prepareStackTrace()?

static optional prepareStackTrace: (err, stackTraces) => any;

Optional override for formatting stack traces

See

https://v8.dev/docs/stack-trace-api#customizing-stack-traces

Parameters

Returns

any

Inherited from

Error.prepareStackTrace

stackTraceLimit

static stackTraceLimit: number;

Inherited from

Error.stackTraceLimit

Methods

captureStackTrace()

static captureStackTrace(targetObject, constructorOpt?): void

Create .stack property on a target object

Parameters

Returns

void

Inherited from

Error.captureStackTrace

CredentialsSignin

Can be thrown from the authorize callback of the Credentials provider. When an error occurs during the authorize callback, two things can happen:

1. The user is redirected to the signin page, with error=CredentialsSignin&code=credentials in the URL. code is configurable.
2. If you throw this error in a framework that handles form actions server-side, this error is thrown, instead of redirecting the user, so you’ll need to handle.

Extends

• SignInError

Constructors

new CredentialsSignin(message, errorOptions)

new CredentialsSignin(message?, errorOptions?): CredentialsSignin

Parameters

Returns

CredentialsSignin

Inherited from

SignInError.constructor

Properties

cause?

optional cause: Record<string, unknown> & {
  err: Error;
};

Type declaration

err?

optional err: Error;

Inherited from

SignInError.cause

code

code: string;

The error code that is set in the code query parameter of the redirect URL.

⚠ NOTE: This property is going to be included in the URL, so make sure it does not hint at sensitive errors.

The full error is always logged on the server, if you need to debug.

Generally, we don’t recommend hinting specifically if the user had either a wrong username or password specifically, try rather something like “Invalid credentials”.

message

message: string;

Inherited from

SignInError.message

name

name: string;

Inherited from

SignInError.name

stack?

optional stack: string;

Inherited from

SignInError.stack

type

type: ErrorType;

The error type. Used to identify the error in the logs.

Inherited from

SignInError.type

kind

static kind: string;

Inherited from

SignInError.kind

prepareStackTrace()?

static optional prepareStackTrace: (err, stackTraces) => any;

Optional override for formatting stack traces

See

https://v8.dev/docs/stack-trace-api#customizing-stack-traces

Parameters

Returns

any

Inherited from

SignInError.prepareStackTrace

stackTraceLimit

static stackTraceLimit: number;

Inherited from

SignInError.stackTraceLimit

type

static type: string;

Methods

captureStackTrace()

static captureStackTrace(targetObject, constructorOpt?): void

Create .stack property on a target object

Parameters

Returns

void

Inherited from

SignInError.captureStackTrace

Account

Usually contains information about the provider being used and also extends TokenSet, which is different tokens returned by OAuth Providers.

Extends

• Partial<TokenEndpointResponse>

Properties

access_token?

optional readonly access_token: string;

Inherited from

Partial.access_token

authorization_details?

optional readonly authorization_details: AuthorizationDetails[];

Inherited from

Partial.authorization_details

expires_at?

optional expires_at: number;

Calculated value based on TokenEndpointResponse.expires_in.

It is the absolute timestamp (in seconds) when the TokenEndpointResponse.access_token expires.

This value can be used for implementing token rotation together with TokenEndpointResponse.refresh_token.

See

• https://authjs.dev/guides/refresh-token-rotation#database-strategy
• https://www.rfc-editor.org/rfc/rfc6749#section-5.1

expires_in?

optional readonly expires_in: number;

Inherited from

Partial.expires_in

id_token?

optional readonly id_token: string;

Inherited from

Partial.id_token

provider

provider: string;

Provider’s id for this account. E.g. “google”. See the full list at https://authjs.dev/reference/core/providers

providerAccountId

providerAccountId: string;

This value depends on the type of the provider being used to create the account.

• oauth/oidc: The OAuth account’s id, returned from the profile() callback.
• email: The user’s email address.
• credentials: id returned from the authorize() callback

refresh_token?

optional readonly refresh_token: string;

Inherited from

Partial.refresh_token

scope?

optional readonly scope: string;

Inherited from

Partial.scope

token_type?

optional readonly token_type: Lowercase<string>;

NOTE: because the value is case insensitive it is always returned lowercased

Inherited from

Partial.token_type

type

type: ProviderType;

Provider’s type for this account

userId?

optional userId: string;

id of the user this account belongs to

See

https://authjs.dev/reference/core/adapters#adapteruser

DefaultSession

Extended by

• Session

Properties

expires

expires: string;

user?

optional user: User;

Profile

The user info returned from your OAuth provider.

See

https://openid.net/specs/openid-connect-core-1_0.html#StandardClaims

Indexable

[claim: string]: unknown

Properties

address?

optional address: null | {
  country: null | string;
  formatted: null | string;
  locality: null | string;
  postal_code: null | string;
  region: null | string;
  street_address: null | string;
};

birthdate?

optional birthdate: null | string;

email?

optional email: null | string;

email_verified?

optional email_verified: null | boolean;

family_name?

optional family_name: null | string;

gender?

optional gender: null | string;

given_name?

optional given_name: null | string;

id?

optional id: null | string;

locale?

optional locale: null | string;

middle_name?

optional middle_name: null | string;

name?

optional name: null | string;

nickname?

optional nickname: null | string;

phone_number?

optional phone_number: null | string;

picture?

optional picture: any;

preferred_username?

optional preferred_username: null | string;

profile?

optional profile: null | string;

sub?

optional sub: null | string;

updated_at?

optional updated_at: null | string | number | Date;

website?

optional website: null | string;

zoneinfo?

optional zoneinfo: null | string;

Session

The active session of the logged in user.

Extends

• DefaultSession

Properties

expires

expires: string;

Inherited from

DefaultSession.expires

user?

optional user: User;

Inherited from

DefaultSession.user

User

The shape of the returned object in the OAuth providers’ profile callback, available in the jwt and session callbacks, or the second parameter of the session callback, when using a database.

Extended by

• AdapterUser

Properties

email?

optional email: null | string;

id?

optional id: string;

image?

optional image: null | string;

name?

optional name: null | string;

customFetch

const customFetch: unique symbol;

This advanced option allows you to override the default fetch function used by the provider to make requests to the provider’s OAuth endpoints.

It can be used to support corporate proxies, custom fetch libraries, cache discovery endpoints, add mocks for testing, logging, set custom headers/params for non-spec compliant providers, etc.

Example

import { Auth, customFetch } from "@auth/core"
import GitHub from "@auth/core/providers/github"
 
const dispatcher = new ProxyAgent("my.proxy.server")
function proxy(...args: Parameters<typeof fetch>): ReturnType<typeof fetch> {
  return undici(args[0], { ...(args[1] ?? {}), dispatcher })
}
 
const response = await Auth(request, {
  providers: [GitHub({ [customFetch]: proxy })]
})

See

• https://undici.nodejs.org/#/docs/api/ProxyAgent?id=example-basic-proxy-request-with-local-agent-dispatcher
• https://authjs.dev/guides/corporate-proxy

SvelteKitAuth()

SvelteKitAuth(config): {
  handle: Handle;
  signIn: Action;
  signOut: Action;
}

The main entry point to @auth/sveltekit

Parameters

Returns

{
  handle: Handle;
  signIn: Action;
  signOut: Action;
}

handle

handle: Handle;

signIn

signIn: Action;

signOut

signOut: Action;

See

https://sveltekit.authjs.dev