Quickstart: SvelteKit

Intro

This example provides the steps to build a simple user management app (from scratch!) using Supabase and Svelte. 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

Whenever you get stuck at any point, take a look at 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 project 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.

Dashboard

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

SQL

-- Create a table for public "profiles"
create table profiles (
  id uuid references auth.users not null,
  updated_at timestamp with time zone,
  username text unique,
  avatar_url text,
  website text,

  primary key (id),
  unique(username),
  constraint username_length check (char_length(username) >= 3)
);

alter table profiles enable row level security;

create policy "Public profiles are viewable by everyone."
  on profiles for select
  using ( true );

create policy "Users can insert their own profile."
  on profiles for insert
  with check ( auth.uid() = id );

create policy "Users can update own profile."
  on profiles for update
  using ( auth.uid() = id );

-- Set up Realtime!
begin;
  drop publication if exists supabase_realtime;
  create publication supabase_realtime;
commit;
alter publication supabase_realtime add table profiles;

-- Set up Storage!
insert into storage.buckets (id, name)
values ('avatars', 'avatars');

create policy "Avatar images are publicly accessible."
  on storage.objects for select
  using ( bucket_id = 'avatars' );

create policy "Anyone can upload an avatar."
  on storage.objects for insert
  with check ( bucket_id = 'avatars' );

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):

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

Then let's install the only additional dependency: 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

VITE_SUPABASE_URL="YOUR_SUPABASE_URL"
VITE_SUPABASE_ANON_KEY="YOUR_SUPABASE_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.

lib/supabaseClient.js

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 public/global.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.

lib/Auth.svelte

<script>
  import {supabase} from "$lib/supabaseClient"

  let loading = false
  let email;

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

<form class="row flex flex-center" on:submit|preventDefault={handleLogin}>
  <div class="col-6 form-widget">
    <h1 class="header">Supabase + Svelte</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>

User store

To access the user information in other places, we use a writable store. Create a new file called sessionStore.js

lib/sessionStore.js

import { writable } from 'svelte/store'

export const user = writable(false)

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 Profile.svelte.

lib/Profile.svelte

<script>
  import { supabase } from '$lib/supabaseClient'
  import { user } from '$lib/sessionStore'

  let loading = true
  let username = null
  let website = null
  let avatar_url = null

  function getProfile(node: HTMLElement) {
  try {
    loading = true;
    const user = supabase.auth.user();

    supabase
      .from("profiles")
      .select(`username, website, avatar_url`)
      .eq("id", user?.id)
      .single()
      .then(({ data, error, status }) => {
        if (data) {
          username = data.username;
          website = data.website;
          avatar_url = data.avatar_url;
        }
        if (error && status !== 406) throw error;
      });
    } catch (error: any) {
      alert(error.message);
    } finally {
      loading = false;
    }
  }

  async function updateProfile() {
    try {
      loading = true
      const user = supabase.auth.user()

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

      let { error } = await supabase.from('profiles').upsert(updates, {
        returning: 'minimal', // Don't return the value after inserting
      })

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

<form use:getProfile class="form-widget" on:submit|preventDefault={updateProfile}>
  <div>
    <label for="email">Email</label>
    <input id="email" type="text" value={$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/index.svelte:

src/routes/index.svelte

<script>
    import {user} from "$lib/sessionStore"
    import {supabase} from "$lib/supabaseClient"
    import Auth from "$lib/Auth.svelte"
    import Profile from "$lib/Profile.svelte"

    user.set(supabase.auth.user())

    supabase.auth.onAuthStateChange((_, session) => {
        user.set(session.user)
    })
</script>

<div class="container" style="padding: 50px 0 100px 0;">
    {#if $user}
        <Profile />
    {:else}
        <Auth />
    {/if}
</div>

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

npm run dev

And then open the browser to localhost:3000 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:

lib/Avatar.svelte

<script>
  import { createEventDispatcher } from 'svelte'
  import { supabase } from '$lib/supabaseClient'

  export let path;
  export let size = "10em"

  let uploading = false
  let src;
  let files;

  const dispatch = createEventDispatcher();

  function downloadImage() {
    supabase.storage
      .from("avatars")
      .download(path)
      .then(({ data, error }) => {
        if (error) throw error;
        src = URL.createObjectURL(data);
      })
      .catch((error) =>
        console.error("Error downloading image: ", error.message)
      );
  }

  async function uploadAvatar() {
    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 fileName = `${Math.random()}.${fileExt}`
      const filePath = `${fileName}`

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

      if (uploadError) throw uploadError
      
      path = filePath
      dispatch('upload')
    } catch (error) {
      alert(error.message)
    } finally {
      uploading = false
    }
  }
</script>

<div>
  {#if path}
    <img use:downloadImage
      {src}
      alt="Avatar"
      class="avatar image"
      style="height: {size}; width: {size};"
    />
  {:else}
    <div class="avatar no-image" style="height: {size}; width: {size};" />
  {/if}
  
  <div style="width: {size};">
    <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:

$lib/Profile.svelte

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

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

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

Next steps

At this stage you have a fully functional application!

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