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warning

@auth/sveltekit is currently experimental. The API will change in the future.

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/core @auth/sveltekit

Usage​

src/hooks.server.ts
import { SvelteKitAuth } from "@auth/sveltekit"
import GitHub from "@auth/core/providers/github"
import { GITHUB_ID, GITHUB_SECRET } from "$env/static/private"

export const handle = SvelteKitAuth({
  providers: [GitHub({ clientId: GITHUB_ID, clientSecret: GITHUB_SECRET })],
})

or to use sveltekit platform environment variables for platforms like Cloudflare

src/hooks.server.ts
import { SvelteKitAuth } from "@auth/sveltekit"
import GitHub from "@auth/core/providers/github"
import type { Handle } from "@sveltejs/kit";

export const handle = SvelteKitAuth(async (event) => {
  const authOptions = {
    providers: [GitHub({ clientId: event.platform.env.GITHUB_ID, clientSecret: event.platform.env.GITHUB_SECRET })]
    secret: event.platform.env.AUTH_SECRET,
    trustHost: true
  }
  return authOptions
}) satisfies Handle;

Don't forget 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.prefix:

[origin]/auth/callback/[provider]

Signing in and signing out​

The data for the current session in this example was made available through the $page store which can be set through the root +page.server.ts file. It is not necessary to store the data there, however, this makes it globally accessible throughout your application simplifying state management.

<script>
  import { signIn, signOut } from "@auth/sveltekit/client"
  import { page } from "$app/stores"
</script>

<h1>SvelteKit Auth Example</h1>
<p>
  {#if $page.data.session}
    {#if $page.data.session.user?.image}
      <span
        style="background-image: url('{$page.data.session.user.image}')"
        class="avatar"
      />
    {/if}
    <span class="signedInText">
      <small>Signed in as</small><br />
      <strong>{$page.data.session.user?.name ?? "User"}</strong>
    </span>
    <button on:click={() => signOut()} class="button">Sign out</button>
  {:else}
    <span class="notSignedInText">You are not signed in</span>
    <button on:click={() => signIn("github")}>Sign In with GitHub</button>
  {/if}
</p>

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.getSession()
  };
};

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.getSession();
  if (!session?.user) throw redirect(303, '/auth');
  return {};
};
danger

Make sure to ALWAYS grab the session information from the parent instead of using the store in the case of a PageLoad. Not doing so can lead to users being able to incorrectly access protected information in the case the +layout.server.ts does not run for that page load. This code sample already implements the correct method by using const { session } = await parent();

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, available in hooks.server.ts, is a function that receives ALL requests sent to your SvelteKit webapp. You may intercept them inside the handle hook, add and modify things in the request, block requests, etc. Some readers may notice we are already using this handle hook for SvelteKitAuth which returns a handle itself, so we are going to use SvelteKit's sequence to provide middleware-like functions that set the handle hook.

import { SvelteKitAuth } from '@auth/sveltekit';
import GitHub from '@auth/core/providers/github';
import { GITHUB_ID, GITHUB_SECRET } from '$env/static/private';
import { redirect, type Handle } from '@sveltejs/kit';
import { sequence } from '@sveltejs/kit/hooks';

async function authorization({ event, resolve }) {
	// Protect any routes under /authenticated
	if (event.url.pathname.startsWith('/authenticated')) {
   const session = await event.locals.getSession();
		if (!session) {
			throw redirect(303, '/auth');
		}
	}

	// 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(
	SvelteKitAuth({
		providers: [GitHub({ clientId: GITHUB_ID, clientSecret: GITHUB_SECRET })]
	}),
	authorization
);
info

Learn more about SvelteKit's handle hooks and sequence here.

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​

info

Learn more about @auth/sveltekit here.

info

PRs to improve this documentation are welcome! See this file.

SvelteKitAuth()​

SvelteKitAuth(options): Handle

The main entry point to @auth/sveltekit

Parameters​

▪ options: SvelteKitAuthConfig | DynamicSvelteKitAuthConfig

Returns​

Handle

See​

https://sveltekit.authjs.dev

SvelteKitAuthConfig​

Configure the SvelteKitAuth method.

Extends​

  • AuthConfig

Properties​

providers​

providers: Provider[]

List of authentication providers for signing in (e.g. Google, Facebook, Twitter, GitHub, Email, etc) in any order. This can be one of the built-in providers or an object with a custom provider.

Default​
[]
Inherited from​

AuthConfig.providers

adapter​

adapter?: Adapter

You can use the adapter option to pass in your database adapter.

Inherited from​

AuthConfig.adapter

callbacks​

callbacks?: Partial<CallbacksOptions<Profile, Account>>

Callbacks are asynchronous functions you can use to control what happens when an action is performed. Callbacks are extremely powerful, especially in scenarios involving JSON Web Tokens as they allow you to implement access controls without a database and to integrate with external databases or APIs.

Inherited from​

AuthConfig.callbacks

cookies​

cookies?: Partial<CookiesOptions>

You can override the default cookie names and options for any of the cookies used by NextAuth.js. You can specify one or more cookies with custom properties, but if you specify custom options for a cookie you must provide all the options for that cookie. If you use this feature, you will likely want to create conditional behavior to support setting different cookies policies in development and production builds, as you will be opting out of the built-in dynamic policy.

  • ⚠ This is an advanced option. Advanced options are passed the same way as basic options, but may have complex implications or side effects. You should try to avoid using advanced options unless you are very comfortable using them.
Default​
{}
Inherited from​

AuthConfig.cookies

debug​

debug?: boolean

Set debug to true to enable debug messages for authentication and database operations.

Default​
false
Inherited from​

AuthConfig.debug

events​

events?: Partial<EventCallbacks>

Events are asynchronous functions that do not return a response, they are useful for audit logging. You can specify a handler for any of these events below - e.g. for debugging or to create an audit log. The content of the message object varies depending on the flow (e.g. OAuth or Email authentication flow, JWT or database sessions, etc), but typically contains a user object and/or contents of the JSON Web Token and other information relevant to the event.

Default​
{}
Inherited from​

AuthConfig.events

jwt​

jwt?: Partial<JWTOptions>

JSON Web Tokens are enabled by default if you have not specified an AuthConfig.adapter. JSON Web Tokens are encrypted (JWE) by default. We recommend you keep this behaviour.

Inherited from​

AuthConfig.jwt

logger​

logger?: Partial<LoggerInstance>

Override any of the logger levels (undefined levels will use the built-in logger), and intercept logs in NextAuth. You can use this option to send NextAuth logs to a third-party logging service.

Example​
// /pages/api/auth/[...nextauth].js
import log from "logging-service"
export default NextAuth({
  logger: {
    error(code, ...message) {
      log.error(code, message)
    },
    warn(code, ...message) {
      log.warn(code, message)
    },
    debug(code, ...message) {
      log.debug(code, message)
    }
  }
})
Default​
console
Inherited from​

AuthConfig.logger

pages​

pages?: Partial<PagesOptions>

Specify URLs to be used if you want to create custom sign in, sign out and error pages. Pages specified will override the corresponding built-in page.

Default​
{}
Example​
  pages: {
    signIn: '/auth/signin',
    signOut: '/auth/signout',
    error: '/auth/error',
    verifyRequest: '/auth/verify-request',
    newUser: '/auth/new-user'
  }
Inherited from​

AuthConfig.pages

prefix​

prefix?: string

Defines the base path for the auth routes. If you change the default value, you must also update the callback URL used by the providers.

Default​

${base}/auth - base is the base path of your SvelteKit app, configured in svelte.config.js.

redirectProxyUrl​

redirectProxyUrl?: string

When set, during an OAuth sign-in flow, the redirect_uri of the authorization request will be set based on this value.

This is useful if your OAuth Provider only supports a single redirect_uri or you want to use OAuth on preview URLs (like Vercel), where you don't know the final deployment URL beforehand.

The url needs to include the full path up to where Auth.js is initialized.

Note​

This will auto-enable the state OAuth2Config.checks on the provider.

Example​
"https://authjs.example.com/api/auth"

You can also override this individually for each provider.

Example​
GitHub({
  ...
  redirectProxyUrl: "https://github.example.com/api/auth"
})
Default​

AUTH_REDIRECT_PROXY_URL environment variable

See also: Guide: Securing a Preview Deployment

Inherited from​

AuthConfig.redirectProxyUrl

secret​

secret?: string

A random string used to hash tokens, sign cookies and generate cryptographic keys. If not specified, it falls back to AUTH_SECRET or NEXTAUTH_SECRET from environment variables. To generate a random string, you can use the following command:

  • On Unix systems, type openssl rand -hex 32 in the terminal
  • Or generate one online
Inherited from​

AuthConfig.secret

session​

session?: object

Configure your session like if you want to use JWT or a database, how long until an idle session expires, or to throttle write operations in case you are using a database.

Type declaration​
generateSessionToken​

generateSessionToken?: () => string

Generate a custom session token for database-based sessions. By default, a random UUID or string is generated depending on the Node.js version. However, you can specify your own custom string (such as CUID) to be used.

Returns​

string

Default​

randomUUID or randomBytes.toHex depending on the Node.js version

maxAge​

maxAge?: number

Relative time from now in seconds when to expire the session

Default​
2592000 // 30 days
strategy​

strategy?: "jwt" | "database"

Choose how you want to save the user session. The default is "jwt", an encrypted JWT (JWE) in the session cookie.

If you use an adapter however, we default it to "database" instead. You can still force a JWT session by explicitly defining "jwt".

When using "database", the session cookie will only contain a sessionToken value, which is used to look up the session in the database.

Documentation | Adapter | About JSON Web Tokens

updateAge​

updateAge?: number

How often the session should be updated in seconds. If set to 0, session is updated every time.

Default​
86400 // 1 day
Inherited from​

AuthConfig.session

theme​

theme?: Theme

Changes the theme of built-in AuthConfig.pages.

Inherited from​

AuthConfig.theme

trustHost​

trustHost?: boolean

Todo​
Inherited from​

AuthConfig.trustHost

useSecureCookies​

useSecureCookies?: boolean

When set to true then all cookies set by NextAuth.js will only be accessible from HTTPS URLs. This option defaults to false on URLs that start with http:// (e.g. http://localhost:3000) for developer convenience. You can manually set this option to false to disable this security feature and allow cookies to be accessible from non-secured URLs (this is not recommended).

  • ⚠ This is an advanced option. Advanced options are passed the same way as basic options, but may have complex implications or side effects. You should try to avoid using advanced options unless you are very comfortable using them.

The default is false HTTP and true for HTTPS sites.

Inherited from​

AuthConfig.useSecureCookies