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Method URL:https://slack.com/api/chat.postEphemeral
Preferred HTTP method:POST
Accepted content types:application/x-www-form-urlencoded, application/json
Rate limiting:Tier 4
Works with:
Token typeRequired scope(s)
userchat:write:user  chat:write:bot 

This method posts an ephemeral message, which is visible only to the assigned user in a specific public channel, private channel, or private conversation.

Ephemeral message delivery is not guaranteed — the user must be currently active in Slack and a member of the specified channel. By nature, ephemeral messages do not persist across reloads, desktop and mobile apps, or sessions.

Use ephemeral messages to send users context-sensitive messages, relevant to the channel they're detectably participating in. Avoid sending unexpected or unsolicited ephemeral messages.


Argument Example Required Description

Authentication token bearing required scopes.

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

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


Channel, private group, or IM channel to send message to. Can be an encoded ID, or a name.

textHello worldRequired

Text of the message to send. See below for an explanation of formatting. This field is usually required, unless you're providing only attachments instead.


id of the user who will receive the ephemeral message. The user should be in the channel specified by the channel argument.


Pass true to post the message as the authed user. Defaults to true if the chat:write:bot scope is not included. Otherwise, defaults to false.

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

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


Find and link channel names and usernames.


Change how messages are treated. Defaults to none. See below.


Provide another message's ts value to post this message in a thread. Avoid using a reply's ts value; use its parent's value instead. Ephemeral messages in threads are only shown if there is already an active thread.

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

A message must have either text or attachments or both. The text parameter is required unless you provide attachments. Use both parameters in conjunction with each other to create awesome messages.


Messages are formatted as described in the formatting spec. You can specify values for parse and link_names to change formatting behavior.

The optional attachments argument should contain a JSON-encoded array of attachments.

For more information, see the attachments spec. If you're using a Slack app, you can also use this method to attach message buttons.

Use the Message Builder to preview your message formatting and attachments in real time! It's easy to translate your JSON examples to the parameters understood by chat.postEphemeral.

For best results, limit the number of characters in the text field to a few thousand bytes at most. Ideally, messages should be short and human-readable, if you need to post longer messages, please consider uploading a snippet instead. (A single message should be no larger than 4,000 bytes.)

Consider reviewing our message guidelines, especially if you're using attachments or message buttons.


How message authorship is attributed varies by a few factors, with some behaviors varying depending on the kinds of tokens you're using to post a message.

The best way to realize your intended result is to be explicit with the as_user parameter.

chat.postEphemeral wants your message posting to succeed and may attempt to guess the most appropriate as_user interpretation based on the kind of token you're using.

If as_user is not provided at all, then the value is inferred, based on the scopes granted to the caller: If the caller could post with as_user passed as false, then that is how the method behaves; otherwise, the method behaves as if as_user were passed as true.

When as_user is false

When the as_user parameter is set to false, messages are posted as "bot_messages", with message authorship attributed to the user name and icons associated with the Slack App.

When as_user is true

Set as_user to true and the authenticated user will appear as the author of the message. Posting as the authenticated user requires the client or the more preferred chat:write:user scopes.

Target channels and users

You must specify a conversation container (public channel, private channel, or an IM channel) by providing its ID to the channel argument. You also must specify a target user.

Each type of channel behaves slightly differently based on the authenticated user's permissions and additional arguments. If the target user is not in the given channel, the ephemeral message will not be delivered, and we'll return a user_not_in_channel error.

Workspace apps will receive a no_permission error when they are not a member of the specified channel.

Note that the user parameter expects a user's id, and not a username or display name.

Post to a public 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 private group

As long as the authenticated user is a member of the private group, you can either pass the group's name (secret-group) or encoded ID (G012AC86C), and the message will be posted to that group. The private group's ID can be retrieved through the groups.list API method.

Post to an IM channel

Posting to an IM channel is a little more complex depending on the value of as_user.

  • If as_user is false:
    • Pass a username (@chris) as the value of channel to post to that user's @slackbot channel as the bot.
    • Pass the IM channel's ID (D023BB3L2) as the value of channel to post to that IM channel as the bot. The IM channel's ID can be retrieved through the im.list API method.
  • If as_user is true:
    • Pass the IM channel's ID (D023BB3L2) as the value of channel to post to that IM channel as the authenticated user. The IM channel's ID can be retrieved through the im.list API method.

To send a direct message to the user owning the token used in the request, provide the channel field with the a conversation/IM ID value found in a method like im.list.


Typical success response

    "ok": true,
    "message_ts": "1502210682.580145"

Typical error response

    "ok": false,
    "error": "user_not_in_channel"

The message_ts included with the response cannot be used with chat.update, as it does not represent an actual message written to the database like it does with other api methods.


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.


A workspace preference prevents the authenticated user from posting.


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


Channel has been archived.


Value passed for channel was invalid.


Message text is too long


No message text provided


Intended recipient is not in the specified channel.


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.