Setting up Server-Side Auth for SvelteKit

Set up Server-Side Auth to use cookie-based authentication with SvelteKit.

Install Supabase packages

Install the @supabase/supabase-js package and the helper @supabase/ssr package.


_10npm install @supabase/supabase-js @supabase/ssr

Set up environment variables

Create a .env.local file in your project root directory.

Fill in your PUBLIC_SUPABASE_URL and PUBLIC_SUPABASE_ANON_KEY:

Project URL

Anon key

.env.local


_10PUBLIC_SUPABASE_URL=<your_supabase_project_url>
_10PUBLIC_SUPABASE_ANON_KEY=<your_supabase_anon_key>

Set up server-side hooks

Set up server-side hooks in src/hooks.server.ts. The hooks:

Create a request-specific Supabase client, using the user credentials from the request cookie. This client is used for server-only code.
Check user authentication.
Guard protected pages.

src/hooks.server.ts


_82import { createServerClient } from '@supabase/ssr'
_82import { type Handle, redirect } from '@sveltejs/kit'
_82import { sequence } from '@sveltejs/kit/hooks'
_82
_82import { PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY } from '$env/static/public'
_82
_82const supabase: Handle = async ({ event, resolve }) => {
_82  /**
_82   * Creates a Supabase client specific to this server request.
_82   *
_82   * The Supabase client gets the Auth token from the request cookies.
_82   */
_82  event.locals.supabase = createServerClient(PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY, {
_82    cookies: {
_82      get: (key) => event.cookies.get(key),
_82      /**
_82       * SvelteKit's cookies API requires `path` to be explicitly set in
_82       * the cookie options. Setting `path` to `/` replicates previous/
_82       * standard behavior.
_82       */
_82      set: (key, value, options) => {
_82        event.cookies.set(key, value, { ...options, path: '/' })
_82      },
_82      remove: (key, options) => {
_82        event.cookies.delete(key, { ...options, path: '/' })
_82      },
_82    },
_82  })
_82
_82  /**
_82   * Unlike `supabase.auth.getSession()`, which returns the session _without_
_82   * validating the JWT, this function also calls `getUser()` to validate the
_82   * JWT before returning the session.
_82   */
_82  event.locals.safeGetSession = async () => {
_82    const {
_82      data: { session },
_82    } = await event.locals.supabase.auth.getSession()
_82    if (!session) {
_82      return { session: null, user: null }
_82    }
_82
_82    const {
_82      data: { user },
_82      error,
_82    } = await event.locals.supabase.auth.getUser()
_82    if (error) {
_82      // JWT validation has failed
_82      return { session: null, user: null }
_82    }
_82
_82    return { session, user }
_82  }
_82
_82  return resolve(event, {
_82    filterSerializedResponseHeaders(name) {
_82      /**
_82       * Supabase libraries use the `content-range` and `x-supabase-api-version`
_82       * headers, so we need to tell SvelteKit to pass it through.
_82       */
_82      return name === 'content-range' || name === 'x-supabase-api-version'
_82    },
_82  })
_82}
_82
_82const authGuard: Handle = async ({ event, resolve }) => {
_82  const { session, user } = await event.locals.safeGetSession()
_82  event.locals.session = session
_82  event.locals.user = user
_82
_82  if (!event.locals.session && event.url.pathname.startsWith('/private')) {
_82    return redirect(303, '/auth')
_82  }
_82
_82  if (event.locals.session && event.url.pathname === '/auth') {
_82    return redirect(303, '/private')
_82  }
_82
_82  return resolve(event)
_82}
_82
_82export const handle: Handle = sequence(supabase, authGuard)

Create TypeScript definitions

To prevent TypeScript errors, add type definitions for the new event.locals properties.

src/app.d.ts


_18import type { Session, SupabaseClient, User } from '@supabase/supabase-js'
_18
_18declare global {
_18  namespace App {
_18    // interface Error {}
_18    interface Locals {
_18      supabase: SupabaseClient
_18      safeGetSession: () => Promise<{ session: Session | null; user: User | null }>
_18      session: Session | null
_18      user: User | null
_18    }
_18    // interface PageData {}
_18    // interface PageState {}
_18    // interface Platform {}
_18  }
_18}
_18
_18export {}

Create a Supabase client in your root layout

Create a Supabase client in your root +layout.ts. This client can be used to access Supabase from the client or the server. In order to get access to the Auth token on the server, use a +layout.server.ts file to pass in the session from event.locals.

src/routes/+layout.ts

src/routes/+layout.server.ts


_51import { createBrowserClient, createServerClient, isBrowser, parse } from '@supabase/ssr'
_51
_51import { PUBLIC_SUPABASE_ANON_KEY, PUBLIC_SUPABASE_URL } from '$env/static/public'
_51
_51import type { LayoutLoad } from './$types'
_51
_51export const load: LayoutLoad = async ({ data, depends, fetch }) => {
_51  /**
_51   * Declare a dependency so the layout can be invalidated, for example, on
_51   * session refresh.
_51   */
_51  depends('supabase:auth')
_51
_51  const supabase = isBrowser()
_51    ? createBrowserClient(PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY, {
_51        global: {
_51          fetch,
_51        },
_51        cookies: {
_51          get(key) {
_51            const cookie = parse(document.cookie)
_51            return cookie[key]
_51          },
_51        },
_51      })
_51    : createServerClient(PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY, {
_51        global: {
_51          fetch,
_51        },
_51        cookies: {
_51          get() {
_51            return JSON.stringify(data.session)
_51          },
_51        },
_51      })
_51
_51  /**
_51   * It's fine to use `getSession` here, because on the client, `getSession` is
_51   * safe, and on the server, it reads `session` from the `LayoutData`, which
_51   * safely checked the session using `safeGetSession`.
_51   */
_51  const {
_51    data: { session },
_51  } = await supabase.auth.getSession()
_51
_51  const {
_51    data: { user },
_51  } = await supabase.auth.getUser()
_51
_51  return { session, supabase, user }
_51}

Listen to Auth events

Set up a listener for Auth events on the client, to handle session refreshes and signouts.

src/routes/+layout.svelte


_28<script>
_28	import { goto, invalidate } from '$app/navigation';
_28	import { onMount } from 'svelte';
_28
_28	export let data;
_28	$: ({ session, supabase } = data);
_28
_28	onMount(() => {
_28		const { data } = supabase.auth.onAuthStateChange((_, newSession) => {
_28			if (!newSession) {
_28				/**
_28				 * Queue this as a task so the navigation won't prevent the
_28				 * triggering function from completing
_28				 */
_28				setTimeout(() => {
_28					goto('/', { invalidateAll: true });
_28				});
_28			}
_28			if (newSession?.expires_at !== session?.expires_at) {
_28				invalidate('supabase:auth');
_28			}
_28		});
_28
_28		return () => data.subscription.unsubscribe();
_28	});
_28</script>
_28
_28<slot />

Create your first page

Create your first page. This example page calls Supabase from the server to get a list of countries from the database.

This is an example of a public page that uses publicly readable data.

To populate your database, run the countries quickstart from your dashboard.

src/routes/+page.server.ts

src/routes/+page.svelte


_10import type { PageServerLoad } from './$types'
_10
_10export const load: PageServerLoad = async ({ locals: { supabase } }) => {
_10  const { data: countries } = await supabase.from('countries').select('name').limit(5).order('name')
_10  return { countries: countries ?? [] }
_10}

Change the Auth confirmation path

If you have email confirmation turned on (the default), a new user will receive an email confirmation after signing up.

Change the email template to support a server-side authentication flow.

Go to the Auth templates page in your dashboard. In the Confirm signup template, change {{ .ConfirmationURL }} to {{ .SiteURL }}/api/auth/confirm?token_hash={{ .TokenHash }}&type=signup.

Create a login page

Next, create a login page to let users sign up and log in.

src/routes/auth/+page.server.ts

src/routes/auth/+page.svelte

src/routes/auth/+layout.svelte

src/routes/auth/error/+page.svelte


_32import { redirect } from '@sveltejs/kit'
_32
_32import type { Actions } from './$types'
_32
_32export const actions: Actions = {
_32  signup: async ({ request, locals: { supabase } }) => {
_32    const formData = await request.formData()
_32    const email = formData.get('email') as string
_32    const password = formData.get('password') as string
_32
_32    const { error } = await supabase.auth.signUp({ email, password })
_32    if (error) {
_32      console.error(error)
_32      return redirect(303, '/auth/error')
_32    } else {
_32      return redirect(303, '/')
_32    }
_32  },
_32  login: async ({ request, locals: { supabase } }) => {
_32    const formData = await request.formData()
_32    const email = formData.get('email') as string
_32    const password = formData.get('password') as string
_32
_32    const { error } = await supabase.auth.signInWithPassword({ email, password })
_32    if (error) {
_32      console.error(error)
_32      return redirect(303, '/auth/error')
_32    } else {
_32      return redirect(303, '/private')
_32    }
_32  },
_32}

Create the signup confirmation route

Finish the signup flow by creating the API route to handle email verification.

src/routes/api/auth/confirm/+server.ts


_31import type { EmailOtpType } from '@supabase/supabase-js'
_31import { redirect } from '@sveltejs/kit'
_31
_31import type { RequestHandler } from './$types'
_31
_31export const GET: RequestHandler = async ({ url, locals: { supabase } }) => {
_31  const token_hash = url.searchParams.get('token_hash')
_31  const type = url.searchParams.get('type') as EmailOtpType | null
_31  const next = url.searchParams.get('next') ?? '/'
_31
_31  /**
_31   * Clean up the redirect URL by deleting the Auth flow parameters.
_31   *
_31   * `next` is preserved for now, because it's needed in the error case.
_31   */
_31  const redirectTo = new URL(url)
_31  redirectTo.pathname = next
_31  redirectTo.searchParams.delete('token_hash')
_31  redirectTo.searchParams.delete('type')
_31
_31  if (token_hash && type) {
_31    const { error } = await supabase.auth.verifyOtp({ type, token_hash })
_31    if (!error) {
_31      redirectTo.searchParams.delete('next')
_31      return redirect(303, redirectTo)
_31    }
_31  }
_31
_31  redirectTo.pathname = '/auth/error'
_31  return redirect(303, redirectTo)
_31}

Create private routes

Create private routes that can only be accessed by authenticated users. The routes in the private directory are protected by the route guard in hooks.server.ts.

To ensure that hooks.server.ts runs for every nested path, put a +layout.server.ts file in the private directory. This file can be empty, but must exist to protect routes that don't have their own +layout|page.server.ts.

src/routes/private/+layout.server.ts

src/routes/private/+layout.svelte

SQL

src/routes/private/+page.server.ts

src/routes/private/+page.svelte


_10/**
_10 * This file is necessary to ensure protection of all routes in the `private`
_10 * directory. It makes the routes in this directory _dynamic_ routes, which
_10 * send a server request, and thus trigger `hooks.server.ts`.
_10 **/