Supabase Realtime Broadcast: Powering Live Collaboration Made Simple

Table of contents:

• Introduction
• What is Supabase Realtime Broadcast?
• Example: Cursor Sharing in Real Time
• Real-World Use Cases
• Advantages
• Conclusion

Introduction

Building real-time collaboration features often feels complex - syncing states, managing websockets, and ensuring low-latency updates. Supabase makes this easier with Realtime Broadcast, a feature that lets you share low-latency messages across connected clients instantly.

What is Supabase Realtime Broadcast?

Realtime Broadcast is part of Supabase’s Realtime engine. Unlike traditional database triggers or storage events, Broadcast is designed specifically for ephemeral client-to-client messages - meaning updates don’t persist in the database, but sync instantly across connected users.

This makes it perfect for collaborative apps where speed and responsiveness matter.

Example: Cursor Sharing in Real Time

Supabase even ships a cursor sharing component in its UI library. With just a few lines of code, you can show other users’ mouse positions in real time - like in Google Docs or Figma.

const channel = supabase.channel('cursor-room')

channel.on('broadcast', { event: 'cursor' }, ({ payload }) => {
  // update cursor position in the UI
})

channel.subscribe()
// send cursor update
channel.send({
  type: 'broadcast',
  event: 'cursor',
  payload: { x: 120, y: 200 },
})

In this snippet:

• Every connected client subscribes to a channel.
• Cursor updates are broadcasted instantly.
• No database writes, no extra setup.

Real-World Use Cases

• Collaborative editing: Multiple users editing the same document.
• Live whiteboards: Shared drawing boards or design tools.
• Gaming: Syncing player movements in multiplayer games.
• Dashboards: Broadcasting live metrics or notifications.

Advantages

• Low-latency messaging without managing websockets manually.
• Ephemeral updates — no unnecessary database writes.
• Simple API built right into Supabase.
• Scales naturally with your existing Supabase project.

Conclusion

Supabase Realtime Broadcast removes the friction from building live collaboration. Whether you’re syncing cursors, chats, or dashboards – it just works out of the box.

If you’ve ever wanted to add that “Google Docs magic” to your product, this feature gives you the foundation without the usual complexity.

👉 Want to dive deeper? Check out the official docs here: Supabase Realtime Broadcast Documentation