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Method URL:https://slack.com/api/mpim.open
Preferred HTTP method:POST
Accepted content types:application/x-www-form-urlencoded, application/json
Rate limiting:Tier 3
Works with:
Token typeRequired scope(s)

This method opens a multiparty direct message.

Opening a multiparty direct message takes a list of up-to 8 encoded user ids. If there is no MPIM already created that includes that exact set of members, a new MPIM will be created. Subsequent calls to mpim.open with the same set of users will return the already existing MPIM conversation.


Argument Example Required Description

Authentication token bearing required scopes.


Comma separated lists of users. The ordering of the users is preserved whenever a MPIM group is returned.

This method supports application/json via HTTP POST. Present your token in your request's Authorization header. Learn more.


If successful, the command returns a mpim object, including state information:

    "ok": true,
    "group": {
        "id": "G024BE91L",
        "name": "mpdm-user--user_a--user_b--user_c-1",
        "is_group": "true",
        "created": 1360782804,
        "creator": "U024BE7LH",
        "is_archived": false,
        "is_open": false,
        "is_mpim": true,
        "last_read": "0000000000.000000",
        "latest": null,
        "unread_count": 0,
        "unread_count_display": 0,
        "members": [
        "topic": {
            "value": "Group messaging.",
            "creator": "U024BE7LH",
            "last_set": 1360782804
        "purpose": {
            "value": "Group messaging with: @user @user_a @user_b @user_c",
            "creator": "U024BE7LH",
            "last_set": 1360782804


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.


Missing users in request


Needs at least 2 users to open


Needs at most 8 users to open


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.


Administrators have suspended the ability to post a message.


The token used is not granted the specific scope permissions required to complete this request.


The method was called with invalid arguments.


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 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/json 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.


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.