Introduction

Getting started with Svelte

#Automatic Setup With Create Instant App

The fastest way to get started with Instant with SvelteKit is to use create-instant-app to scaffold a new project with Instant already set up.

To get started run:

npx create-instant-app --sv

#Manual Setup

Create a blank SvelteKit app:

npx sv create my-app

Add the InstantDB Svelte Library:

npm i @instantdb/svelte

Use instant-cli to set up a new Instant project. This will prompt you to log in if you haven't already. It will then create a schema file, permissions file, and update your .env file.

npx instant-cli init

Create a database client in src/lib/db.ts:

src/lib/db.ts

import { init } from '@instantdb/svelte';
import schema from '../instant.schema';
 
export const db = init({
  appId: import.meta.env.VITE_INSTANT_APP_ID!,
  schema,
  useDateObjects: true,
});

You're now ready to make queries and transactions to your database!

#Creating a To-Do List App

Let's add a "todo" entity to our schema file at src/instant.schema.ts:

src/instant.schema.ts

import { i } from '@instantdb/svelte';
 
const _schema = i.schema({
  entities: {
    $files: i.entity({
      path: i.string().unique().indexed(),
      url: i.string(),
    }),
    $users: i.entity({
      email: i.string().unique().indexed().optional(),
      imageURL: i.string().optional(),
      type: i.string().optional(),
    }),
    todos: i.entity({
      text: i.string(),
      done: i.boolean(),
      createdAt: i.date(),
    }),
  },
  links: {
    $usersLinkedPrimaryUser: {
      forward: {
        on: '$users',
        has: 'one',
        label: 'linkedPrimaryUser',
        onDelete: 'cascade',
      },
      reverse: {
        on: '$users',
        has: 'many',
        label: 'linkedGuestUsers',
      },
    },
  },
  rooms: {},
});
 
//...

Push the schema:

npx instant-cli push

Instant doesn't support SSR with SvelteKit yet (let us know if you want this!) so you need to disable SSR for routes that use Instant.

src/routes/+page.ts

export const ssr = false;

Replace the content of src/routes/+page.svelte with the following:

src/routes/+page.svelte

<script lang="ts">
  import { id, type InstaQLEntity } from '@instantdb/svelte';
  import { db } from '$lib/db';
  import type { AppSchema } from '../instant.schema';
 
  type Todo = InstaQLEntity<AppSchema, 'todos'>;
 
  const query = db.useQuery({ todos: {} });
 
  let text = $state('');
 
  function addTodo(todoText: string) {
    db.transact(
      db.tx.todos[id()].update({
        text: todoText,
        done: false,
        createdAt: Date.now(),
      }),
    );
  }
 
  function deleteTodo(todo: Todo) {
    db.transact(db.tx.todos[todo.id].delete());
  }
 
  function toggleDone(todo: Todo) {
    db.transact(db.tx.todos[todo.id].update({ done: !todo.done }));
  }
 
  function deleteCompleted(todos: Todo[]) {
    const completed = todos.filter((todo) => todo.done);
    if (completed.length === 0) return;
    const txs = completed.map((todo) => db.tx.todos[todo.id].delete());
    db.transact(txs);
  }
</script>
 
{#if query.isLoading}
<div>Loading...</div>
{:else if query.error}
<div>Error: {query.error.message}</div>
{:else} {@const todos = query.data?.todos ?? []}
<div>
  <h2>Todos</h2>
  <div>
    <form onsubmit={(e) => {
      e.preventDefault(); if (!text) return; addTodo(text); text = '';
    }}>
      <input
        bind:value={text}
        autofocus
        placeholder="What needs to be done?"
        type="text"
      />
    </form>
    {#each todos as todo (todo.id)}
    <div>
      <input type="checkbox" checked={todo.done} onchange={() =>
        toggleDone(todo)} />
      <span class:line-through={todo.done}>{todo.text}</span>
      <button onclick={() => deleteTodo(todo)}>X</button>
    </div>
    {/each}
    <div>
      Remaining todos: {todos.filter((t) => !t.done).length}
      <button onclick={() =>
        deleteCompleted(todos)}> Delete Completed
      </button>
    </div>
  </div>
</div>
{/if}

Go to localhost:5173, and huzzah 🎉 You've got a fully functional todo list running!

#Reactivity

In Svelte 5, Instant's hooks return $state proxies. You read properties directly off the returned object, and Svelte automatically tracks them for re-rendering.

<script lang="ts">
  const query = db.useQuery({ todos: {} });
  // query.isLoading, query.data, query.error are all reactive
</script>
 
{#if !query.isLoading}
<p>{query.data?.todos.length} todos</p>
{/if}

For primitive values like connection status and local IDs, hooks return a { current: value } wrapper (since primitives cannot be $state proxies):

<script lang="ts">
  const status = db.useConnectionStatus();
  // status.current is reactive
</script>
 
<p>Connection: {status.current}</p>

#Reactive and conditional queries

You can pass a function to useQuery to make queries reactive or conditional. The function will be re-evaluated whenever its dependencies change. Return null to skip the query:

<script lang="ts">
  import { db } from '$lib/db';
 
  const auth = db.useAuth();
 
  // Only query when we have a logged-in user
  const query = db.useQuery(() =>
    auth.user ? { todos: {} } : null
  );
</script>
 
{#if auth.isLoading}
  <p>Loading...</p>
{:else if !auth.user}
  <p>Please log in.</p>
{:else if query.isLoading}
  <p>Loading todos...</p>
{:else}
  {@const todos = query.data?.todos ?? []}
  <p>{todos.length} todos</p>
{/if}

This also works for reactive parameters. Any $state variable read inside the function will automatically trigger a new query when it changes:

<script lang="ts">
  import { db } from '$lib/db';
 
  let filter = $state<'all' | 'active' | 'done'>('all');
 
  const query = db.useQuery(() => {
    if (filter === 'all') return { todos: {} };
    return { todos: { $: { where: { done: filter === 'done' } } } };
  });
</script>
 
<button onclick={() => filter = 'all'}>All</button>
<button onclick={() => filter = 'active'}>Active</button>
<button onclick={() => filter = 'done'}>Done</button>

#Writing data

Transactions in Svelte work the same way they do in React via db.transact:

<script lang="ts">
  import { id } from '@instantdb/svelte';
  import { db } from '$lib/db';
 
  function addTodo(text: string) {
    db.transact(db.tx.todos[id()].update({ text, done: false, createdAt: Date.now() }));
  }
 
  function toggleDone(todo: { id: string; done: boolean }) {
    db.transact(db.tx.todos[todo.id].update({ done: !todo.done }));
  }
 
  function deleteTodo(todoId: string) {
    db.transact(db.tx.todos[todoId].delete());
  }
</script>

To learn more see our writing data docs.

#Auth

The Svelte SDK supports all of Instant's auth methods: magic codes, guest auth, Google OAuth, and more.

#useAuth

Use db.useAuth() to get the current auth state. This gives you full control over loading, error, and user states:

<script lang="ts">
  import { db } from '$lib/db';
 
  const auth = db.useAuth();
</script>
 
{#if auth.isLoading}
  <div>Loading...</div>
{:else if auth.error}
  <div>Error: {auth.error.message}</div>
{:else if auth.user}
  <div>
    <p>Hello, {auth.user.isGuest ? 'Guest' : auth.user.email}!</p>
    <button onclick={() => db.auth.signOut()}>Sign out</button>
  </div>
{:else}
  <div>
    <p>Please log in.</p>
    <button onclick={() => db.auth.signInAsGuest()}>
      Try as guest
    </button>
  </div>
{/if}

#SignedIn / SignedOut

For simpler cases where you just need to gate content on auth state, you can use the SignedIn and SignedOut guard components instead:

<script lang="ts">
  import { SignedIn, SignedOut } from '@instantdb/svelte';
  import { db } from '$lib/db';
</script>
 
<SignedIn {db}>
  <p>You are logged in!</p>
  <button onclick={() => db.auth.signOut()}>Sign out</button>
</SignedIn>
 
<SignedOut {db}>
  <p>Please log in.</p>
</SignedOut>

useAuth is better when you need access to isLoading, error, or user.isGuest. The guard components are simpler when you just need to show or hide content based on login state.

#Components

#Cursors

A multiplayer cursor component that tracks mouse positions via presence. Wrap any area where you want to show live cursors from other users:

<script lang="ts">
  import { Cursors } from '@instantdb/svelte';
  import { db } from '$lib/db';
 
  const room = db.room('main', 'my-room-id');
</script>
 
<Cursors {room} userCursorColor="tomato">
  <div>Move your mouse around!</div>
</Cursors>

The Cursors component supports custom cursor rendering via a renderCursor snippet, a configurable wrapper element (as), and className/style props for styling. See the Presence, Cursors, and Activity docs for more details.

Next: Create Instant App