Realtime Concepts

Supabase Realtime lets you to build real-time applications with collaborative/multiplayer functionality. It includes 3 core features:

• Broadcast: sends rapid, ephemeral messages to other connected clients. You can use it to track mouse movements, for example.
• Presence: sends user state between connected clients. You can use it to show an "online" status, which disappears when a user is disconnected.
• Postgres Changes: receives database changes in real-time.

Channels#

When you initialize your Supabase Realtime client, you define a topic that uniquely references a channel. Everyone connected to the same Channel topic receives the same messages.

Clients can bi-directionally send and receive messages over a Channel. The Realtime backend can also push messages to all clients connected to the same Channel.

A single client can receive change records from Postgres, Broadcast messages from other clients, and Presence updates all over the same Channel.

Choosing between Broadcast and Presence#

We recommend using Broadcast by default, and then Presence when required. Presence merges all changes into a shared state for every client connected to the same channel. If you use Presence, it's best to throttle your changes so that you are sending updates less frequently.