Browser

Get a SpacetimeDB app running in the browser with inline JavaScript.

Prerequisites

• Node.js 18+ installed
• SpacetimeDB CLI installed

Install the SpacetimeDB CLI before continuing.

Create your project

Run the spacetime dev command to create a new project with a TypeScript SpacetimeDB module.

This will start the local SpacetimeDB server, publish your module, and generate TypeScript client bindings.

spacetime dev --template browser-ts 
    

Build the client bindings

The generated TypeScript bindings need to be bundled into a JavaScript file that can be loaded in the browser via a script tag.

cd my-spacetime-app
npm install
npm run build 
    

Open in browser

Open index.html directly in your browser. The app connects to SpacetimeDB and displays data in real-time.

The JavaScript code runs inline in a script tag, using the bundled DbConnection class.

<!-- Load the bundled bindings -->
<script src="dist/bindings.iife.js"></script>

<script>
  const HOST = 'ws://localhost:3000';
  const DB_NAME = 'my-spacetime-app';
  const TOKEN_KEY = `${HOST}/${DB_NAME}/auth_token`;

  const conn = DbConnection.builder()
    .withUri(HOST)
    .withDatabaseName(DB_NAME)
    .withToken(localStorage.getItem(TOKEN_KEY))
    .onConnect((conn, identity, token) => {
      localStorage.setItem(TOKEN_KEY, token);
      console.log('Connected:', identity.toHexString());

      // Subscribe to tables
      conn.subscriptionBuilder()
        .onApplied(() => {
          for (const person of conn.db.person.iter()) {
            console.log(person.name);
          }
        })
        .subscribe(tables.person);
    })
    .build();
</script> 
    

Call reducers

Reducers are functions that modify data — they're the only way to write to the database.

// Call a reducer with named arguments
conn.reducers.add({ name: 'Alice' }); 
    

React to changes

Register callbacks to update your UI when data changes.

conn.db.person.onInsert((ctx, person) => {
  console.log('New person:', person.name);
});

conn.db.person.onDelete((ctx, person) => {
  console.log('Removed:', person.name);
}); 
    

Next steps

• See the Chat App Tutorial for a complete example
• Read the TypeScript SDK Reference for detailed API docs