Build a User Management App with Svelte

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.

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#

1. Create a new project in the Supabase Dashboard.
2. Enter your project details.
3. 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 Project URL and anon key from the API settings.

1. Go to the API Settings page in the Dashboard.
2. 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 Vite Svelte TypeScript Template to initialize an app called supabase-svelte:

1npm create vite@latest supabase-svelte -- --template svelte-ts
2cd supabase-svelte
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 API URL and the anon key that you copied earlier.

1VITE_SUPABASE_URL=YOUR_SUPABASE_URL
2VITE_SUPABASE_ANON_KEY=YOUR_SUPABASE_ANON_KEY

Now that we have the API credentials in place, let's create a 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/supabase-js'

const supabaseUrl = import.meta.env.VITE_SUPABASE_URL
const supabaseAnonKey = import.meta.env.VITE_SUPABASE_ANON_KEY

export const supabase = createClient(supabaseUrl, supabaseAnonKey)

And one optional step is to update the CSS file src/app.css to make the app look nice. You can find the full contents of this file here.

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.

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

  let loading = false
  let email = ''

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

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

Account page#

After a user is signed in we can allow them to edit their profile details and manage their account. Let's create a new component for that called Account.svelte.

<script lang="ts">
  import { onMount } from "svelte";
  import type { AuthSession } from "@supabase/supabase-js";
  import { supabase } from "../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 (error && status !== 406) throw error

      if (data) {
        username = data.username
        website = data.website
        avatarUrl = data.avatar_url
      }
    } catch (error) {
      if (error instanceof Error) {
        alert(error.message)
      }
    } finally {
      loading = false
    }
  }

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

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

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

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

<form on:submit|preventDefault={updateProfile} class="form-widget">
  <div>Email: {session.user.email}</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="text" bind:value={website} />
  </div>
  <div>
    <button type="submit" class="button primary block" disabled={loading}>
      {loading ? 'Saving ...' : 'Update profile'}
    </button>
  </div>
  <button type="button" class="button block" on:click={() => supabase.auth.signOut()}>
    Sign Out
  </button>
</form>

Launch!#

Now that we have all the components in place, let's update App.svelte:

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

  let session: AuthSession

  onMount(() => {
    supabase.auth.getSession().then(({ data }) => {
      session = data.session
    })

    supabase.auth.onAuthStateChange((_event, _session) => {
      session = _session
    })
  })
</script>

<div class="container" style="padding: 50px 0 100px 0">
  {#if !session}
  <Auth />
  {:else}
  <Account {session} />
  {/if}
</div>

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.

⚠️ WARNING: Svelte uses Vite and the default port is 5173, Supabase uses port 3000. To change the redirection port for supabase go to: Authentication > Settings and change the Site Url to localhost:5173

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:

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

  export let size: number
  export let url: string

  let avatarUrl: string = 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 style="width: {size}px" aria-live="polite">
  {#if avatarUrl} <img src={avatarUrl} alt={avatarUrl ? 'Avatar' : 'No image'} class="avatar image"
  style="height: {size}px, width: {size}px" /> {:else}
  <div class="avatar no-image" style="height: {size}px, width: {size}px" />
  {/if}
  <div style="width: {size}px">
    <label class="button primary block" for="single">
      {uploading ? 'Uploading ...' : 'Upload avatar'}
    </label>
    <span style="display:none">
      <input
        type="file"
        id="single"
        accept="image/*"
        bind:files
        on:change="{uploadAvatar}"
        disabled="{uploading}"
      />
    </span>
  </div>
</div>

Add the new widget#

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

<script lang="ts">
  // Import the new component
  import Avatar from './Avatar.svelte'
</script>

<form on:submit|preventDefault="{updateProfile}" class="form-widget">
  <!-- Add to body -->
  <Avatar bind:url="{avatarUrl}" size="{150}" 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 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!