Quickstart: SvelteKit

This example provides the steps to build a basic user management app. It includes:

• Supabase Database: a Postgres database for storing your user data.
• Supabase Auth: users can sign in with magic links (no passwords, only email).
• Supabase Storage: users can upload a photo.
• Row Level Security: data is protected so that individuals can only access their own data.
• Instant APIs: APIs will be automatically generated when you create your database tables.

By the end of this guide you'll have an app which allows users to login and update some basic profile details:

GitHub#

Should you get stuck while working through the guide, refer to this repo.

Project set up

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#

1. Go to app.supabase.com.
2. Click on "New Project".
3. Enter your project details.
4. 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.

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 URL and anon key from the API settings.

1. Go to the Settings page in the Dashboard.
2. Click API in the sidebar.
3. Find your API 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 you do not need TypeScript, ESLint, Prettier, or Playwright):

1npm init svelte@next supabase-sveltekit
2cd supabase-sveltekit
3npm install

Then let's install the only additional dependency: supabase-js

1npm 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.

1PUBLIC_SUPABASE_URL="YOUR_SUPABASE_URL"
2PUBLIC_SUPABASE_ANON_KEY="YOUR_SUPABASE_KEY"

Now that we have the API credentials in place, create a src/lib/supabaseClient.ts helper file to initialize the Supabase client. These variables will be exposed on the browser, and that's completely fine since we have Row Level Security enabled on our Database.

import { createClient } from '@supabase/auth-helpers-sveltekit'
import { env } from '$env/dynamic/public'

export const supabase = createClient(env.PUBLIC_SUPABASE_URL, env.PUBLIC_SUPABASE_ANON_KEY)

Optionally, update src/routes/style.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:

1npm install @supabase/auth-helpers-sveltekit

Update your src/routes/+layout.svelte:

<script lang="ts">
  import { supabase } from '$lib/supabaseClient'
  import { invalidate } from '$app/navigation'
  import { onMount } from 'svelte'
  import './styles.css'

  onMount(() => {
    const {
      data: { subscription },
    } = supabase.auth.onAuthStateChange(() => {
      invalidate('supabase:auth')
    })

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

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

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

import type { LayoutLoad } from './$types'
import { getSupabase } from '@supabase/auth-helpers-sveltekit'

export const load: LayoutLoad = async (event) => {
  const { session } = await getSupabase(event)
  return { session }
}

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

import type { LayoutServerLoad } from './$types'
import { getServerSession } from '@supabase/auth-helpers-sveltekit'

export const load: LayoutServerLoad = async (event) => {
  return {
    session: await getServerSession(event),
  }
}

Be sure to create src/hooks.client.ts and src/hooks.server.ts in order to get the auth helper started on the client and server-side.

import '$lib/supabaseClient'

import '$lib/supabaseClient'

Set up a Login component#

Let's set up a Svelte component to manage logins and sign ups. We'll use Magic Links, so users can sign in with their email without using passwords. Create a new Auth.svelte component in the src/routes directory to handle this functionality.

<script lang="ts">
  import { supabase } from '$lib/supabaseClient'

  let loading = false
  let email: string

  const handleLogin = async () => {
    try {
      loading = true
      const { error } = await supabase.auth.signInWithOtp({ email })
      if (error) throw error
      alert('Check your email for the login link!')
    } catch (error) {
      if (error instanceof Error) {
        alert(error.message)
      }
    } finally {
      loading = false
    }
  }
</script>

<form class="row flex-center flex" on:submit|preventDefault="{handleLogin}">
  <div class="col-6 form-widget">
    <h1 class="header">Supabase + SvelteKit</h1>
    <p class="description">Sign in via magic link with your email below</p>
    <div>
      <input class="inputField" type="email" placeholder="Your email" bind:value="{email}" />
    </div>
    <div>
      <input type="submit" class="button block" value={loading ? 'Loading' : 'Send magic link'}
      disabled={loading} />
    </div>
  </div>
</form>

Account component#

After a user is signed in, they need to be able to edit their profile details and manage their account. Create a new Account.svelte component in the src/routes directory to handle this functionality.

<script lang="ts">
  import { onMount } from 'svelte'
  import type { AuthSession } from '@supabase/supabase-js'
  import { supabase } from '$lib/supabaseClient'

  export let session: AuthSession

  let loading = false
  let username: string | null = null
  let website: string | null = null
  let avatarUrl: string | null = null

  onMount(() => {
    getProfile()
  })

  const getProfile = async () => {
    try {
      loading = true
      const { user } = session

      const { data, error, status } = await supabase
        .from('profiles')
        .select(`username, website, avatar_url`)
        .eq('id', user.id)
        .single()

      if (data) {
        username = data.username
        website = data.website
        avatarUrl = data.avatar_url
      }

      if (error && status !== 406) throw error
    } catch (error) {
      if (error instanceof Error) {
        alert(error.message)
      }
    } finally {
      loading = false
    }
  }

  async function updateProfile() {
    try {
      loading = true
      const { user } = session

      const updates = {
        id: user.id,
        username,
        website,
        avatar_url: avatarUrl,
        updated_at: new Date(),
      }

      let { error } = await supabase.from('profiles').upsert(updates)

      if (error) throw error
    } catch (error) {
      if (error instanceof Error) {
        alert(error.message)
      }
    } finally {
      loading = false
    }
  }

  async function signOut() {
    try {
      loading = true
      let { error } = await supabase.auth.signOut()
      if (error) throw error
    } catch (error) {
      if (error instanceof Error) {
        alert(error.message)
      }
    } finally {
      loading = false
    }
  }
</script>

<form class="form-widget" on:submit|preventDefault="{updateProfile}">
  <div>
    <label for="email">Email</label>
    <input id="email" type="text" value="{session.user.email}" disabled />
  </div>
  <div>
    <label for="username">Name</label>
    <input id="username" type="text" bind:value="{username}" />
  </div>
  <div>
    <label for="website">Website</label>
    <input id="website" type="website" bind:value="{website}" />
  </div>

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

  <div>
    <button class="button block" on:click="{signOut}" disabled="{loading}">Sign Out</button>
  </div>
</form>

Launch!#

Now that we have all the components in place, let's update src/routes/+page.svelte:

<script>
  import { page } from '$app/stores'
  import Account from './Account.svelte'
  import Auth from './Auth.svelte'
</script>

<svelte:head>
  <title>Supabase + SvelteKit</title>
  <meta name="description" content="SvelteKit using supabase-js v2" />
</svelte:head>

{#if !$page.data.session}
<Auth />
{:else}
<Account session="{$page.data.session}" />
{/if}

Once that's done, run this in a terminal window:

1npm 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.

Create an upload widget#

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 directory:

<script lang="ts">
  import { createEventDispatcher } from 'svelte'
  import { supabase } from '$lib/supabaseClient'

  export let size = 10
  export let url: string

  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
      dispatch('upload')
    } 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}

  <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>

Add the new widget#

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

<script>
  // Import the new component
  import Avatar from './Avatar.svelte'
</script>

<form use:getProfile class="form-widget" on:submit|preventDefault="{updateProfile}">
  <!-- Add to body -->
  <Avatar bind:url="{avatarUrl}" size="{10}" on:upload="{updateProfile}" />

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

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

create or replace function delete_avatar(avatar_url text, out status int, out content varchar)
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 $$
declare
  status int;
  content varchar;
begin
  if coalesce(old.avatar_url, '') <> ''
      and (tg_op = 'DELETE' or (old.avatar_url <> new.avatar_url)) then
    select
      into status, content
      result.status, result.content
      from public.delete_avatar(old.avatar_url) as result;
    if status <> 200 then
      raise warning 'Could not delete avatar: % %', status, content;
    end if;
  end if;
  if tg_op = 'DELETE' then
    return old;
  end if;
  return new;
end;
$$;

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();

Next steps#

At this stage you have a fully functional application!

• Got a question? Ask here.
• Sign in: app.supabase.com