Public channels

A channel is public when its name does not start with private- or presence-. Any client holding the app key can subscribe to it, and the app key ships in your client code, so treat a public channel as readable by anyone who can open your site.

代码示例

const orders = bird.subscribe("orders");
orders.bind("order-updated", (data) => {
  console.log(data);
});

There is nothing to create or configure. The channel exists while at least one connection is subscribed and disappears when the last one leaves.

When to use one

Use a public channel for data that is already public, or that is harmless to expose: build status, a live scoreboard, flight information, the number of people viewing a page, a status-page incident feed.

Do not use one for anything scoped to a user or a tenant. If the data belongs to one account, the channel name is not a secret and guessing it is trivial. Use a private channel instead.

What public channels cannot do

No member identity. Public channels have no members, so no bird:member_added or bird:member_removed events and no member list. Those belong to presence channels.
No client events. A client cannot send client- events on a public channel. The edge rejects them with Client event rejected - only supported on private and presence channels.

Connection counting works on any channel type. When the app has it enabled, the client receives bird:connection_count with the number of connections currently subscribed.

Naming

Channel names allow letters, digits, and _ - = @ , . ; up to 164 characters. Names are case-sensitive and matched exactly, so Orders and orders are two channels.

Because a public channel name is visible to every client, keep identifiers out of it that you would not want enumerated. orders is fine. orders-user-4821 is a public channel whose name tells anyone that user 4821 exists.

Next steps

Private channels restrict subscription to clients your backend approves.
Publishing events covers publishing from your server, including broadcasting to many channels.
Realtime overview explains channels, members, and connections.