Schedules a message to be sent to a channel.

This method schedules a message for delivery to a public channel, private channel, or direct message/IM channel at a specified time in the future.



Authentication token bearing required scopes. Tokens should be passed as an HTTP Authorization header or alternatively, as a POST parameter.


Channel, private group, or DM channel to send message to. Can be an encoded ID, or a name. See below for more details.


Unix EPOCH timestamp of time in future to send the message.


How this field works and whether it is required depends on other fields you use in your API call. See below for more detail.

ExampleHello world

Pass true to post the message as the authed user, instead of as a bot. Defaults to false. See chat.postMessage.


A JSON-based array of structured attachments, presented as a URL-encoded string.

Example[{"pretext": "pre-hello", "text": "text-world"}]

A JSON-based array of structured blocks, presented as a URL-encoded string.

Example[{"type": "section", "text": {"type": "plain_text", "text": "Hello world"}}]

Find and link channel names and usernames.


Change how messages are treated. Defaults to none. See chat.postMessage.


Used in conjunction with thread_ts and indicates whether reply should be made visible to everyone in the channel or conversation. Defaults to false.


Provide another message's ts value to make this message a reply. Avoid using a reply's ts value; use its parent instead.


Pass true to enable unfurling of primarily text-based content.


Pass false to disable unfurling of media content.


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

The post_at arg is a Unix EPOCH timestamp, representing the time the message should post to Slack in the future.

With the exception of the additional post_at argument, this method behaves identically to chat.postMessage. Peruse that page for in-depth documentation on each parameter that this method accepts.

Using text with blocks or attachments

The usage of the text field changes depending on whether you're using blocks. If you are using blocks, this is used as a fallback string to display in notifications. If you aren't, this is the main body text of the message. It can be formatted as plain text, or with mrkdwn.

The text field is not enforced as required when using blocks or attachments. However, we highly recommended that you include text to provide a fallback when using blocks, as described above.


You will only be able to schedule a message up to 120 days into the future. If you specify a post_at timestamp beyond this limit, you’ll receive a time_too_far error response.


Common successful response

Typical success response

    "ok": true,
    "channel": "C1H9RESGL",
    "scheduled_message_id": "Q1298393284",
    "post_at": "1562180400",
    "message": {
        "text": "Here's a message for you in the future",
        "username": "ecto1",
        "bot_id": "B19LU7CSY",
        "attachments": [
                "text": "This is an attachment",
                "id": 1,
                "fallback": "This is an attachment's fallback"
        "type": "delayed_message",
        "subtype": "bot_message"
Common error response

Typical error response if the post_at is invalid (ex. in the past or too far into the future)

    "ok": false,
    "error": "time_in_past"

The response includes the scheduled_message_id assigned to your message. Use it with the chat.deleteScheduledMessage method to delete the message before it is sent.

For details on formatting, usage in threads, and rate limiting, check out chat.postMessage documentation.


You must specify a public channel, private channel, or an IM channel with the channel argument. Each one behaves slightly differently based on the authenticated user's permissions and additional arguments:

Post to a channel

You can either pass the channel's name (#general) or encoded ID (C024BE91L), and the message will be posted to that channel. The channel's ID can be retrieved through the channels.list API method.

Post to a DM

Pass the IM channel's ID (D023BB3L2) or a user's ID (U0G9QF9C6) as the value of channel to post to that IM channel as the app. The IM channel's ID can be retrieved through the im.list API method.

You might receive a channel_not_found error if your app doesn't have permission to enter into an IM with the intended user.


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.


value passed for post_time was invalid.


value passed for post_time was in the past.


value passed for post_time was too far into the future.


Value passed for channel was invalid.


Cannot post user messages to a channel they are not in.


Channel has been archived.


Message text is too long


No message text provided


A workspace preference prevents the authenticated user from posting.


Cannot post any message into a read-only channel.


Cannot post top-level messages into a thread-only channel.


Cannot post thread replies into a non_threadable channel.


Too many attachments were provided with this message. A maximum of 100 attachments are allowed on a message.


Application has posted too many messages, read the Rate Limit documentation for more information


Admin has disabled Slack File sharing in all Slack Connect communications


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 when using a bot token.


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


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 token type used in this request is not allowed.


The method has been deprecated.


The endpoint has been deprecated.


Two factor setup is required.


The method cannot be called from an Enterprise.


The token used is not granted the specific workspace access required to complete this request.


The method was either called with invalid arguments or some detail about the arguments passed are invalid, which is more likely when using complex arguments like blocks or attachments.


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 an array as an argument. Please only input valid strings.


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 request has been ratelimited. Refer to the Retry-After header for when to retry the request.


Access to this method is limited on the current network


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


The service is temporarily unavailable


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.


The server could not complete your operation(s) without encountering an error, likely due to a transient issue on our end. 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 text field of a message should have no more than 40,000 characters. We truncate really long messages.


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.

Sample code

Bolt is a foundational framework that makes it faster and easier to build Slack apps with the platform's latest features.

Scheduling a message in Python

Show code to initialize app
# Create a timestamp for tomorrow at 9AM tomorrow = + datetime.timedelta(days=1) scheduled_time = datetime.time(hour=9, minute=30) schedule_timestamp = datetime.datetime.combine(tomorrow, scheduled_time).strftime('%s') # Channel you want to post message to channel_id = "C12345" try: # Call the chat.scheduleMessage method using the WebClient result = client.chat_scheduleMessage( channel=channel_id, text="Looking towards the future", post_at=schedule_timestamp ) # Log the result except SlackApiError as e: logger.error("Error scheduling message: {}".format(e))

New to building Slack apps with Python? Read Getting Started with Bolt for Python.

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