Public channel

A public channel is a Pusher-protocol channel type that any client with a valid app key can subscribe to without an auth callback. Channel names carry no special prefix. Anything without private- or presence- at the start is public.

Why it matters

Public channels are the simplest real-time primitive. No auth route. No signed token. Open a WebSocket, send a pusher:subscribe frame, and the service starts delivering events. This makes them well-suited for genuinely public real-time surfaces: a public live ticker, a build-status feed, a leaderboard visible to anonymous visitors, an unauthenticated demo of a real-time feature.

The flip side: there is no access control at the protocol layer. Anyone holding the app key can subscribe to any channel name. If you need access control, switch to a private channel or a presence channel. Do not rely on obscure channel names as a substitute for auth.

How it works

A subscribe frame for a public channel carries only the channel name. The service confirms the subscription with pusher_internal:subscription_succeeded and starts forwarding any matching broadcast events.

{ "event": "pusher:subscribe", "data": { "channel": "live-ticker-eurusd" } }

The service does not call out to the application server during the handshake. The publisher remains authenticated against the service (HTTP requests are signed with the app secret), so the only thing that is public is the read side of the channel.

A common pattern is to mix public and private channels in the same app. Marketing pages subscribe to public channels for non-sensitive live data. Authenticated routes subscribe to private channels for per-user data. The same client connection carries both.

Related terms

See also