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This method begins a Real Time Messaging API session and reserves your application a specific URL with which to connect via websocket.

Unlike rtm.start, this method is focused only on connecting to the RTM API.

Use this method in conjunction with other Web API methods like channels.list, users.list, and team.info to build a full picture of the team or workspace you're connecting on behalf of.

Please consult the RTM API documentation for full details on using the RTM API.


Argument Example Required Description
token xxxx-xxxxxxxxx-xxxx Required

Authentication token bearing required scopes.

batch_presence_aware 1 Optional, default=false

Batch presence deliveries via subscription. Enabling changes the shape of presence_change events. See batch presence.

presence_sub true Optional, default=true

Only deliver presence events when requested by subscription. See presence subscriptions.

Present arguments as parameters in application/x-www-form-urlencoded querystring or POST body. This method does not currently accept application/json.


This method returns a WebSocket Message Server URL and limited information about the team:

Typical success response

    "ok": true,
    "self": {
        "id": "U4X318ZMZ",
        "name": "robotoverlord"
    "team": {
        "domain": "slackdemo",
        "id": "T2U81E2FP",
        "name": "SlackDemo"
    "url": "wss://..."

Typical error response

    "ok": false,
    "error": "invalid_auth"

The url property contains a WebSocket Message Server URL. Connecting to this URL will initiate a Real Time Messaging session. These URLs are only valid for 30 seconds, so connect quickly!

The self property contains a small amount of information concerning the connecting user — an id and their name.

The team attribute also houses brief information about the team, including its id, name, domain, and if it's part of an Enterprise Grid, the corresponding enteprise_id.


This table lists the expected errors that this method could return. However, other errors can be returned in the case where the service is down or other unexpected factors affect processing. Callers should always check the value of the ok params in the response.

Error Description

No authentication token provided.


Some aspect of authentication cannot be validated. Either the provided token is invalid or the request originates from an IP address disallowed from making the request.


Authentication token is for a deleted user or workspace.


Authentication token is for a deleted user or workspace or the app has been removed.


The workspace token used in this request does not have the permissions necessary to complete the request. Make sure your app is a member of the conversation it's attempting to post a message to.


The workspace is undergoing an enterprise migration and will not be available until migration is complete.


The method was passed an argument whose name falls outside the bounds of accepted or expected values. This includes very long names and names with non-alphanumeric characters other than _. If you get this error, it is typically an indication that you have made a very malformed API call.


The method was passed a PHP-style array argument (e.g. with a name like foo[7]). These are never valid with the Slack API.


The method was called via a POST request, but the charset specified in the Content-Type header was invalid. Valid charset names are: utf-8 iso-8859-1.


The method was called via a POST request with Content-Type application/x-www-form-urlencoded or multipart/form-data, but the form data was either missing or syntactically invalid.


The method was called via a POST request, but the specified Content-Type was invalid. Valid types are: application/x-www-form-urlencoded multipart/form-data text/plain.


The method was called via a POST request and included a data payload, but the request did not include a Content-Type header.


The workspace associated with your request is currently undergoing migration to an Enterprise Organization. Web API and other platform operations will be intermittently unavailable until the transition is complete.


The method was called via a POST request, but the POST data was either missing or truncated.


The server could not complete your operation(s) without encountering a catastrophic error. It's possible some aspect of the operation succeeded before the error was raised.


This table lists the expected warnings that this method will return. However, other warnings can be returned in the case where the service is experiencing unexpected trouble.

Warning Description

The method was called via a POST request, and recommended practice for the specified Content-Type is to include a charset parameter. However, no charset was present. Specifically, non-form-data content types (e.g. text/plain) are the ones for which charset is recommended.


The method was called via a POST request, and the specified Content-Type is not defined to understand the charset parameter. However, charset was in fact present. Specifically, form-data content types (e.g. multipart/form-data) are the ones for which charset is superfluous.

Argument Value
token Required Generate tokens to test with here.
batch_presence_aware Optional, default=false
presence_sub Optional, default=true
Extra args