Channels and events

Channel types

Prefix	Who can subscribe	Use it for
(none), e.g. news	Anyone with your key	Public updates
private-	Clients your server authorizes	Per-user or per-team data
private-encrypted-	Clients your server authorizes; payloads are end-to-end encrypted	Sensitive data
presence-	Clients your server authorizes, with user info	“Who’s online”, member lists

Channel names can use letters, numbers and _ - = @ , . ;, up to 200 characters.

Authorizing private and presence channels

When a client subscribes to a private- or presence- channel, pusher-js calls your auth endpoint. Sign the request with your server library:

// Express example
app.post('/pusher/auth', (req, res) => {
  const { socket_id, channel_name } = req.body;
  // check the signed-in user may join channel_name, then:
  const auth = channel_name.startsWith('presence-')
    ? pusher.authorizeChannel(socket_id, channel_name, { user_id: req.user.id, user_info: { name: req.user.name } })
    : pusher.authorizeChannel(socket_id, channel_name);
  res.send(auth);
});

Presence

Presence channels tell every member who else is there: pusher:subscription_succeeded gives the current members, then pusher:member_added and pusher:member_removed follow as people join and leave. A user with several tabs open counts once. Up to 100 members per presence channel.

Client events

Turn on Client events in the app’s settings to let clients send events straight to each other (typing indicators, cursors). The event name must start with client-, and they work on private and presence channels only. Each connection can send up to 10 client events a second.

Sending to one user

After a client signs in (pusher.signin() with your server’s authenticateUser), your server can message every connection of that user with pusher.sendToUser(userId, 'event', data) or disconnect them with terminateUserConnections(userId).

Message size

Event data can be up to 10 KB. A trigger can go to up to 100 channels, and a batch can hold up to 10 events.