New ways to connect to the RTM API

Update 2017-07-12: As promised, the latest fields within rtm.start's channel objects are no longer returned. Additionally, the unread_count and unread_count_display channel fields are also missing, though they can still be found in Let us know if this does you undue injury or distress.

rtm.start began life as a broker and bootstrap to Websocket connections established by Slack's desktop and mobile clients. Whenever our clients needed more information to establish state, those fields would get stuffed into the cacophony that is rtm.start's opening salvos.

As team sizes and feature complexity has grown, delivering this immense quantity of information about nearly every user, channel, and conversation on a team has become more difficult to compute, consume, or continue.

It is in this spirit we offer a friendlier alternative in rtm.connect, a method born with the sole purpose of reserving a websocket connection and providing your application its URL.

rtm.start must evolve to continue functioning well for all teams and apps. We strongly recommend using rtm.connect to establish your connections alongside Web API methods to build your app's understanding of the users, channels, and conversations within a team.

One such change coming to rtm.start is the elimination of the latest attribute assigned to each channel in its response.

On July 11, 2017 we'll no longer return these latest fields. If your app needs a channel's latest timestamp value, use to retrieve it instead.

You can test this future behavior in rtm.start today by providing the no_latest=1 parameter.

What's changing?

The short version:

  • We introduced rtm.connect, an improved light-weight way to connect to the RTM API.
  • You can expect growing pains on rtm.start from here on out.
  • We recommend using rtm.connect in conjunction with the Web API to avoid those pains.
  • channel objects in rtm.starts will no longer include the latest attribute after July 11, 2017.
  • Use the new no_latest=1 parameter with rtm.start to preview this behavior today.

The new rtm.connect method yields a satisfyingly short yet useful response:

    "ok": true,
    "url": "wss:\/\/\/websocket\/2I5yBpcvk",
    "team": {
        "id": "T654321",
        "name": "Librarian Society of Soledad",
        "domain": "libsocos",
        "enterprise_id": "E234567",
        "enterprise_name": "Intercontinental Librarian Society"
    "self": {
        "id": "W123456",
        "name": "brautigan"

What isn't changing?

  • We're not deprecating rtm.start at this time, but we strongly encourage you to move away from it and to expect continued changes to maintain its scalability.
  • The websocket connection established for your app is the same regardless of which method is chosen.

How do I prepare?

The tactics to follow vary on your situation:

Only using rtm.start to connect?

We encourage you to review your code and libraries to understand how the initial fields returned by rtm.start are or are not used. If your app only uses the url field, you should be able to safely move to rtm.connect with no further modifications being necessary.

Using some of the data in rtm.start?

If using at least some of the additional data provided by rtm.start, we recommend moving on to determining if you use the latest timestamp field attached to channel objects. If you don't, start using the no_latest=1 parameter to help speed up your connections and consider retrieving all the data you need from the Web API instead and moving to rtm.connect.

Using the latest field from channel objects in rtm.start?

If you're using the latest field, you'll definitely want to act. Start by collecting information about the channels your app is invested in from the Web API using a combination of channels.list and

Then start using the no_latest=1 parameter when connecting with rtm.start, or move to rtm.connect entirely.

The Events API is an attractive alternative to everything RTM API.

When is this happening?

rtm.connect is available today! rtm.start's no_latest=1 parameter is also functional, so you can get started testing the future today.

On July 11, 2017 we will remove the latest attribute from channel objects appearing in all rtm.start responses.

As always, please contact us if you have any questions or concerns.