You joined a channel

Facts

Works with

RTM
{
    "type": "channel_joined",
    "channel": {
        ...
    }
}

The channel_joined event is sent to all connections for a user when that user joins a channel.

In addition to this message, all existing members of the channel may receive a channel_join message event.

There's also the fresher, more dependable member_joined_channel. This changelog entry clears it all up.

When an event occurs, we will send an HTTP POST request to your Request URL. The outer payload is uniform across all Events API methods, and contains fields like team_id and event. Learn more