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.

note

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.

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.

Supabase Auth Helpers#

SvelteKit is a highly versatile framework offering pre-rendering at build time (SSG), server-side rendering at request time (SSR), API routes, and more.

It can be challenging to authenticate your users in all these different environments, that's why we've created the Supabase Auth Helpers to make user management and data fetching within SvelteKit as easy as possible.

Install the auth helpers for SvelteKit:

npm install @supabase/auth-helpers-sveltekit

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 { createSupabaseServerClient } from '@supabase/auth-helpers-sveltekit'
import type { Handle } from '@sveltejs/kit'
export const handle: Handle = async ({ event, resolve }) => {
  event.locals.supabase = createSupabaseServerClient({
    supabaseUrl: PUBLIC_SUPABASE_URL,
    supabaseKey: PUBLIC_SUPABASE_ANON_KEY,
    event,
  })
  /**
   * A convenience helper so we can just call await getSession() instead const { data: { session } } = await supabase.auth.getSession()
   */
  event.locals.getSession = async () => {
    const {
      data: { session },
    } = await event.locals.supabase.auth.getSession()
    return session
  }
  return resolve(event, {
    filterSerializedResponseHeaders(name) {
      return name === 'content-range'
    },
  })
}

If you are using TypeScript the compiler might complain about event.locals.supabase and event.locals.getSession, 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
      getSession(): Promise<Session | null>
    }
    interface PageData {
      session: Session | 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
export const load = async ({ locals: { getSession } }) => {
  return {
    session: await getSession(),
  }
}

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 { invalidate } from '$app/navigation'
import { PUBLIC_SUPABASE_ANON_KEY, PUBLIC_SUPABASE_URL } from '$env/static/public'
import { createSupabaseLoadClient } from '@supabase/auth-helpers-sveltekit'
export const load = async ({ fetch, data, depends }) => {
  depends('supabase:auth')
  const supabase = createSupabaseLoadClient({
    supabaseUrl: PUBLIC_SUPABASE_URL,
    supabaseKey: PUBLIC_SUPABASE_ANON_KEY,
    event: { fetch },
    serverSession: data.session,
  })
  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, _session) => {
			if (_session?.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"
			redirectTo={`${data.url}/auth/callback`}
			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: { getSession } }) => {
  const session = await getSession()
  // if the user is already logged in return them to the account page
  if (session) {
    throw redirect(303, '/account')
  }
  return { url: url.origin }
}

Proof Key for Code Exchange (PKCE)#

As we are employing Proof Key for Code Exchange (PKCE) in our authentication flow, it is necessary to create a server endpoint responsible for exchanging the code for a session.

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

Retrieve the code sent back from the Supabase Auth server using the code query parameter.
Exchange this code for a session, which we store in our chosen storage mechanism (in this case, cookies).
Finally, we redirect the user to the account page.

// src/routes/auth/callback/+server.js
import { redirect } from '@sveltejs/kit'
export const GET = async ({ url, locals: { supabase } }) => {
  const code = url.searchParams.get('code')
  if (code) {
    await supabase.auth.exchangeCodeForSession(code)
  }
  throw redirect(303, '/account')
}

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, type SubmitFunction } from '$app/forms'
	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'
export const load = async ({ locals: { supabase, getSession } }) => {
  const session = await getSession()
  if (!session) {
    throw 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 = {
  update: async ({ request, locals: { supabase, getSession } }) => {
    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 getSession()
    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, getSession } }) => {
    const session = await getSession()
    if (session) {
      await supabase.auth.signOut()
      throw 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.

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}`
			let { 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>

Storage management#

If you upload additional profile photos, they'll accumulate in the avatars bucket because of their random names with only the latest being referenced from public.profiles and the older versions getting orphaned.

To automatically remove obsolete storage objects, extend the database triggers. Note that it is not sufficient to delete the objects from the storage.objects table because that would orphan and leak the actual storage objects in the S3 backend. Instead, invoke the storage API within Postgres via the http extension.

Enable the http extension for the extensions schema in the Dashboard. Then, define the following SQL functions in the SQL Editor to delete storage objects via the API:

create or replace function delete_storage_object(bucket text, object text, out status int, out content text)
returns record
language 'plpgsql'
security definer
as $$
declare
  project_url text := '<YOURPROJECTURL>';
  service_role_key text := '<YOURSERVICEROLEKEY>'; --  full access needed
  url text := project_url||'/storage/v1/object/'||bucket||'/'||object;
begin
  select
      into status, content
           result.status::int, result.content::text
      FROM extensions.http((
    'DELETE',
    url,
    ARRAY[extensions.http_header('authorization','Bearer '||service_role_key)],
    NULL,
    NULL)::extensions.http_request) as result;
end;
$$;
create or replace function delete_avatar(avatar_url text, out status int, out content text)
returns record
language 'plpgsql'
security definer
as $$
begin
  select
      into status, content
           result.status, result.content
      from public.delete_storage_object('avatars', avatar_url) as result;
end;
$$;

Next, add a trigger that removes any obsolete avatar whenever the profile is updated or deleted:

create or replace function delete_old_avatar()
returns trigger
language 'plpgsql'
security definer
as $$
declare
  status int;
  content text;
begin
  if coalesce(old.avatar_url, '') <> ''
      and (tg_op = 'DELETE' or (old.avatar_url <> new.avatar_url)) then
    select
      into status, content
      result.status, result.content
      from public.delete_avatar(old.avatar_url) as result;
    if status <> 200 then
      raise warning 'Could not delete avatar: % %', status, content;
    end if;
  end if;
  if tg_op = 'DELETE' then
    return old;
  end if;
  return new;
end;
$$;
create trigger before_profile_changes
  before update of avatar_url or delete on public.profiles
  for each row execute function public.delete_old_avatar();

Finally, delete the public.profile row before a user is deleted. If this step is omitted, you won't be able to delete users without first manually deleting their avatar image.

create or replace function delete_old_profile()
returns trigger
language 'plpgsql'
security definer
as $$
begin
  delete from public.profiles where id = old.id;
  return old;
end;
$$;
create trigger before_delete_user
  before delete on auth.users
  for each row execute function public.delete_old_profile();

At this stage you have a fully functional application!

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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#

Supabase Auth Helpers#

Supabase Auth UI

Proof Key for Code Exchange (PKCE)#

Account page#

Launch!#

Bonus: Profile photos#

Create an upload widget#

Add the new widget#

Storage management#

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#

Supabase Auth Helpers#

Set up a Login page#

Supabase Auth UI

Proof Key for Code Exchange (PKCE)#

Account page#

Launch!#

Bonus: Profile photos#

Create an upload widget#

Add the new widget#

Storage management#