Build a User Management App with SvelteKit

This tutorial demonstrates how to build a basic user management app. The app authenticates and identifies the user, stores their profile information in the database, and allows the user to log in, update their profile details, and upload a profile photo. The app uses:

Supabase Database - a Postgres database for storing your user data and Row Level Security so data is protected and users can only access their own information.
Supabase Auth - users log in through magic links sent to their email (without having to set up passwords).
Supabase Storage - users can upload a profile photo.

Supabase User Management example

If you get stuck while working through this guide, refer to the full example on GitHub.

Project setup

Before we start building we're going to set up our Database and API. This is as simple as starting a new Project in Supabase and then creating a "schema" inside the database.

Create a project

Create a new project in the Supabase Dashboard.
Enter your project details.
Wait for the new database to launch.

Set up the database schema

Now we are going to set up the database schema. We can use the "User Management Starter" quickstart in the SQL Editor, or you can just copy/paste the SQL from below and run it yourself.

Go to the SQL Editor page in the Dashboard.
Click User Management Starter.
Click Run.

You can easily pull the database schema down to your local project by running the db pull command. Read the local development docs for detailed instructions.

supabase link --project-ref <project-id>
# You can get <project-id> from your project's dashboard URL: https://supabase.com/dashboard/project/<project-id>
supabase db pull

Get the API Keys

Now that you've created some database tables, you are ready to insert data using the auto-generated API. We just need to get the Project URL and anon key from the API settings.

Go to the API Settings page in the Dashboard.
Find your Project URL, anon, and service_role keys on this page.

Building the app

Let's start building the Svelte app from scratch.

Initialize a Svelte app

We can use the SvelteKit Skeleton Project to initialize an app called supabase-sveltekit (for this tutorial we will be using TypeScript):

npm create svelte@latest supabase-sveltekit
cd supabase-sveltekit
npm install

Then install the Supabase client library: supabase-js

npm install @supabase/supabase-js

And finally we want to save the environment variables in a .env. All we need are the SUPABASE_URL and the SUPABASE_KEY key that you copied earlier.

.env

PUBLIC_SUPABASE_URL="YOUR_SUPABASE_URL"
PUBLIC_SUPABASE_ANON_KEY="YOUR_SUPABASE_KEY"

Optionally, add src/styles.css with the CSS from the example.

Creating a Supabase client for SSR:

The ssr package configures Supabase to use Cookies, which is required for server-side languages and frameworks.

Install the Supabase packages:

npm install @supabase/ssr @supabase/supabase-js

Creating a Supabase client with the ssr package automatically configures it to use Cookies. This means your user's session is available throughout the entire SvelteKit stack - page, layout, server, hooks.

Add the code below to your src/hooks.server.ts to initialize the client on the server:

src/hooks.server.ts

// src/hooks.server.ts
import { PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY } from '$env/static/public'
import { createServerClient } from '@supabase/ssr'
import type { Handle } from '@sveltejs/kit'

export const handle: Handle = async ({ event, resolve }) => {
  event.locals.supabase = createServerClient(PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY, {
    cookies: {
      getAll: () => event.cookies.getAll(),
      /**
       * SvelteKit's cookies API requires `path` to be explicitly set in
       * the cookie options. Setting `path` to `/` replicates previous/
       * standard behavior.
       */
      setAll: (cookiesToSet) => {
        cookiesToSet.forEach(({ name, value, options }) => {
          event.cookies.set(name, value, { ...options, path: '/' })
        })
      },
    },
  })

  /**
   * Unlike `supabase.auth.getSession()`, which returns the session _without_
   * validating the JWT, this function also calls `getUser()` to validate the
   * JWT before returning the session.
   */
  event.locals.safeGetSession = async () => {
    const {
      data: { session },
    } = await event.locals.supabase.auth.getSession()
    if (!session) {
      return { session: null, user: null }
    }

    const {
      data: { user },
      error,
    } = await event.locals.supabase.auth.getUser()
    if (error) {
      // JWT validation has failed
      return { session: null, user: null }
    }

    return { session, user }
  }

  return resolve(event, {
    filterSerializedResponseHeaders(name) {
      return name === 'content-range' || name === 'x-supabase-api-version'
    },
  })
}

Note that auth.getSession reads the auth token and the unencoded session data from the local storage medium. It doesn't send a request back to the Supabase Auth server unless the local session is expired.

You should never trust the unencoded session data if you're writing server code, since it could be tampered with by the sender. If you need verified, trustworthy user data, call auth.getUser instead, which always makes a request to the Auth server to fetch trusted data.

If you are using TypeScript the compiler might complain about event.locals.supabase and event.locals.safeGetSession, this can be fixed by updating your src/app.d.ts with the content below:

src/app.d.ts

// src/app.d.ts

import { SupabaseClient, Session } from '@supabase/supabase-js'

declare global {
  namespace App {
    interface Locals {
      supabase: SupabaseClient
      safeGetSession(): Promise<{ session: Session | null; user: User | null }>
    }
    interface PageData {
      session: Session | null
      user: User | null
    }
    // interface Error {}
    // interface Platform {}
  }
}

Create a new src/routes/+layout.server.ts file to handle the session on the server-side.

src/routes/+layout.server.ts

// src/routes/+layout.server.ts
import type { LayoutServerLoad } from './$types'

export const load: LayoutServerLoad = async ({ locals: { safeGetSession }, cookies }) => {
  const { session, user } = await safeGetSession()

  return {
    session,
    user,
    cookies: cookies.getAll(),
  }
}

Start your dev server (npm run dev) in order to generate the ./$types files we are referencing in our project.

Create a new src/routes/+layout.ts file to handle the session and the supabase object on the client-side.

src/routes/+layout.ts

// src/routes/+layout.ts
import { createBrowserClient, createServerClient, isBrowser } from '@supabase/ssr'
import { PUBLIC_SUPABASE_ANON_KEY, PUBLIC_SUPABASE_URL } from '$env/static/public'
import type { LayoutLoad } from './$types'

export const load: LayoutLoad = async ({ fetch, data, depends }) => {
  depends('supabase:auth')

  const supabase = isBrowser()
    ? createBrowserClient(PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY, {
        global: {
          fetch,
        },
      })
    : createServerClient(PUBLIC_SUPABASE_URL, PUBLIC_SUPABASE_ANON_KEY, {
        global: {
          fetch,
        },
        cookies: {
          getAll() {
            return data.cookies
          },
        },
      })

  /**
   * It's fine to use `getSession` here, because on the client, `getSession` is
   * safe, and on the server, it reads `session` from the `LayoutData`, which
   * safely checked the session using `safeGetSession`.
   */
  const {
    data: { session },
  } = await supabase.auth.getSession()

  return { supabase, session }
}

Update your src/routes/+layout.svelte:

src/routes/+layout.svelte

<!-- src/routes/+layout.svelte -->
<script lang="ts">
	import '../styles.css'
	import { invalidate } from '$app/navigation'
	import { onMount } from 'svelte'

	export let data

	let { supabase, session } = data
	$: ({ supabase, session } = data)

	onMount(() => {
		const { data } = supabase.auth.onAuthStateChange((event, newSession) => {
			if (newSession?.expires_at !== session?.expires_at) {
				invalidate('supabase:auth')
			}
		})

		return () => data.subscription.unsubscribe()
	})
</script>

<svelte:head>
	<title>User Management</title>
</svelte:head>

<div class="container" style="padding: 50px 0 100px 0">
	<slot />
</div>

Supabase Auth UI

We can use the Supabase Auth UI, a pre-built Svelte component, for authenticating users via OAuth, email, and magic links.

Install the Supabase Auth UI for Svelte

npm install @supabase/auth-ui-svelte @supabase/auth-ui-shared

Add the Auth component to your home page

src/routes/+page.svelte

<!-- src/routes/+page.svelte -->
<script lang="ts">
	import { Auth } from '@supabase/auth-ui-svelte'
	import { ThemeSupa } from '@supabase/auth-ui-shared'

	export let data
</script>

<svelte:head>
	<title>User Management</title>
</svelte:head>

<div class="row flex-center flex">
	<div class="col-6 form-widget">
		<Auth
			supabaseClient={data.supabase}
			view="magic_link"
			showLinks={false}
			appearance={{ theme: ThemeSupa, style: { input: 'color: #fff' } }}
		/>
	</div>
</div>

Create a src/routes/+page.server.ts file that will return our website URL to be used in our redirectTo above.

// src/routes/+page.server.ts
import { redirect } from '@sveltejs/kit'
import type { PageServerLoad } from './$types'

export const load: PageServerLoad = async ({ url, locals: { safeGetSession } }) => {
  const { session } = await safeGetSession()

  // if the user is already logged in return them to the account page
  if (session) {
    redirect(303, '/account')
  }

  return { url: url.origin }
}

Email template

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=email.

Confirmation endpoint

As we are working in a server-side rendering (SSR) environment, it is necessary to create a server endpoint responsible for exchanging the token_hash for a session.

In the following code snippet, we perform the following steps:

Retrieve the token_hash sent back from the Supabase Auth server using the token_hash query parameter.
Exchange this token_hash for a session, which we store in storage (in this case, cookies).
Finally, the user is redirected to the account page or the error page.

// src/routes/api/auth/confirm/+server.js
import type { EmailOtpType } from '@supabase/supabase-js'
import { redirect } from '@sveltejs/kit'

import type { RequestHandler } from './$types'

export const GET: RequestHandler = async ({ url, locals: { supabase } }) => {
  const token_hash = url.searchParams.get('token_hash')
  const type = url.searchParams.get('type') as EmailOtpType | null
  const next = url.searchParams.get('next') ?? '/account'

  /**
   * Clean up the redirect URL by deleting the Auth flow parameters.
   *
   * `next` is preserved for now, because it's needed in the error case.
   */
  const redirectTo = new URL(url)
  redirectTo.pathname = next
  redirectTo.searchParams.delete('token_hash')
  redirectTo.searchParams.delete('type')

  if (token_hash && type) {
    const { error } = await supabase.auth.verifyOtp({ type, token_hash })
    if (!error) {
      redirectTo.searchParams.delete('next')
      return redirect(303, redirectTo)
    }
  }

  redirectTo.pathname = '/auth/error'
  return redirect(303, redirectTo)
}

Authentication error page

If there is an error with confirming the token you will be redirect to this error page.

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

<p>Login error</p>

Account page

After a user is signed in, they need to be able to edit their profile details and manage their account. Create a new src/routes/account/+page.svelte file with the content below.

src/routes/account/+page.svelte

<!-- src/routes/account/+page.svelte -->
<script lang="ts">
	import { enhance } from '$app/forms';
	import type { SubmitFunction } from '@sveltejs/kit';

	export let data
	export let form

	let { session, supabase, profile } = data
	$: ({ session, supabase, profile } = data)

	let profileForm: HTMLFormElement
	let loading = false
	let fullName: string = profile?.full_name ?? ''
	let username: string = profile?.username ?? ''
	let website: string = profile?.website ?? ''
	let avatarUrl: string = profile?.avatar_url ?? ''

	const handleSubmit: SubmitFunction = () => {
		loading = true
		return async () => {
			loading = false
		}
	}

	const handleSignOut: SubmitFunction = () => {
		loading = true
		return async ({ update }) => {
			loading = false
			update()
		}
	}
</script>

<div class="form-widget">
	<form
		class="form-widget"
		method="post"
		action="?/update"
		use:enhance={handleSubmit}
		bind:this={profileForm}
	>
		<div>
			<label for="email">Email</label>
			<input id="email" type="text" value={session.user.email} disabled />
		</div>

		<div>
			<label for="fullName">Full Name</label>
			<input id="fullName" name="fullName" type="text" value={form?.fullName ?? fullName} />
		</div>

		<div>
			<label for="username">Username</label>
			<input id="username" name="username" type="text" value={form?.username ?? username} />
		</div>

		<div>
			<label for="website">Website</label>
			<input id="website" name="website" type="url" value={form?.website ?? website} />
		</div>

		<div>
			<input
				type="submit"
				class="button block primary"
				value={loading ? 'Loading...' : 'Update'}
				disabled={loading}
			/>
		</div>
	</form>

	<form method="post" action="?/signout" use:enhance={handleSignOut}>
		<div>
			<button class="button block" disabled={loading}>Sign Out</button>
		</div>
	</form>
</div>

Now create the associated src/routes/account/+page.server.ts file that will handle loading our data from the server through the load function and handle all our form actions through the actions object.

import { fail, redirect } from '@sveltejs/kit'
import type { Actions, PageServerLoad } from './$types'

export const load: PageServerLoad = async ({ locals: { supabase, safeGetSession } }) => {
  const { session } = await safeGetSession()

  if (!session) {
    redirect(303, '/')
  }

  const { data: profile } = await supabase
    .from('profiles')
    .select(`username, full_name, website, avatar_url`)
    .eq('id', session.user.id)
    .single()

  return { session, profile }
}

export const actions: Actions = {
  update: async ({ request, locals: { supabase, safeGetSession } }) => {
    const formData = await request.formData()
    const fullName = formData.get('fullName') as string
    const username = formData.get('username') as string
    const website = formData.get('website') as string
    const avatarUrl = formData.get('avatarUrl') as string

    const { session } = await safeGetSession()

    const { error } = await supabase.from('profiles').upsert({
      id: session?.user.id,
      full_name: fullName,
      username,
      website,
      avatar_url: avatarUrl,
      updated_at: new Date(),
    })

    if (error) {
      return fail(500, {
        fullName,
        username,
        website,
        avatarUrl,
      })
    }

    return {
      fullName,
      username,
      website,
      avatarUrl,
    }
  },
  signout: async ({ locals: { supabase, safeGetSession } }) => {
    const { session } = await safeGetSession()
    if (session) {
      await supabase.auth.signOut()
      redirect(303, '/')
    }
  },
}

Launch!

Now that we have all the pages in place, run this in a terminal window:

npm run dev

And then open the browser to localhost:5173 and you should see the completed app.

Supabase Svelte

Bonus: Profile photos

Every Supabase project is configured with Storage for managing large files like photos and videos.

Let's create an avatar for the user so that they can upload a profile photo. We can start by creating a new component called Avatar.svelte in the src/routes/account directory:

src/routes/account/Avatar.svelte

<!-- src/routes/account/Avatar.svelte -->
<script lang="ts">
	import type { SupabaseClient } from '@supabase/supabase-js'
	import { createEventDispatcher } from 'svelte'

	export let size = 10
	export let url: string
	export let supabase: SupabaseClient

	let avatarUrl: string | null = null
	let uploading = false
	let files: FileList

	const dispatch = createEventDispatcher()

	const downloadImage = async (path: string) => {
		try {
			const { data, error } = await supabase.storage.from('avatars').download(path)

			if (error) {
				throw error
			}

			const url = URL.createObjectURL(data)
			avatarUrl = url
		} catch (error) {
			if (error instanceof Error) {
				console.log('Error downloading image: ', error.message)
			}
		}
	}

	const uploadAvatar = async () => {
		try {
			uploading = true

			if (!files || files.length === 0) {
				throw new Error('You must select an image to upload.')
			}

			const file = files[0]
			const fileExt = file.name.split('.').pop()
			const filePath = `${Math.random()}.${fileExt}`

			const { error } = await supabase.storage.from('avatars').upload(filePath, file)

			if (error) {
				throw error
			}

			url = filePath
			setTimeout(() => {
				dispatch('upload')
			}, 100)
		} catch (error) {
			if (error instanceof Error) {
				alert(error.message)
			}
		} finally {
			uploading = false
		}
	}

	$: if (url) downloadImage(url)
</script>

<div>
	{#if avatarUrl}
		<img
			src={avatarUrl}
			alt={avatarUrl ? 'Avatar' : 'No image'}
			class="avatar image"
			style="height: {size}em; width: {size}em;"
		/>
	{:else}
		<div class="avatar no-image" style="height: {size}em; width: {size}em;" />
	{/if}
	<input type="hidden" name="avatarUrl" value={url} />

	<div style="width: {size}em;">
		<label class="button primary block" for="single">
			{uploading ? 'Uploading ...' : 'Upload'}
		</label>
		<input
			style="visibility: hidden; position:absolute;"
			type="file"
			id="single"
			accept="image/*"
			bind:files
			on:change={uploadAvatar}
			disabled={uploading}
		/>
	</div>
</div>

And then we can add the widget to the Account page:

src/routes/account/+page.svelte

<!-- src/routes/account/+page.svelte -->
<script lang="ts">
  // Import the new component
  import Avatar from './Avatar.svelte'
</script>

<div class="form-widget">
  <form
    class="form-widget"
    method="post"
    action="?/update"
    use:enhance={handleSubmit}
    bind:this={profileForm}
  >
    <!-- Add to body -->
    <Avatar
        {supabase}
        bind:url={avatarUrl}
        size={10}
        on:upload={() => {
          profileForm.requestSubmit();
        }}
      />

    <!-- Other form elements -->
  </form>
</div>

At this stage you have a fully functional application!

Build a User Management App with SvelteKit

Project setup

Create a project

Set up the database schema

Get the API Keys

Building the app

Initialize a Svelte app

Creating a Supabase client for SSR:

Supabase Auth UI

Email template

Confirmation endpoint

Authentication error page

Account page

Launch!

Bonus: Profile photos

Create an upload widget

Add the new widget

Is this helpful?

Build a User Management App with SvelteKit

Project setup#

Create a project#

Set up the database schema#

Get the API Keys#

Building the app#

Initialize a Svelte app#

Creating a Supabase client for SSR:#

Set up a login page#

Supabase Auth UI#

Email template#

Confirmation endpoint#

Authentication error page#

Account page#

Launch!#

Bonus: Profile photos#

Create an upload widget#

Add the new widget#

Is this helpful?

Project setup

Create a project

Set up the database schema

Get the API Keys

Building the app

Initialize a Svelte app

Creating a Supabase client for SSR:

Set up a login page

Supabase Auth UI

Email template

Confirmation endpoint

Authentication error page

Account page

Launch!

Bonus: Profile photos

Create an upload widget

Add the new widget