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.
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 default user name and icons associated with the Custom Integration or 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:userscopes.
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. If the user specified as the intended recipient is not in the given channel, the ephemeral message will not be delivered, and a user_not_in_channel error will be returned. Note that the user parameter expects a user's id, and not a screen 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.
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.
Value passed for channel was invalid.
Channel has been archived.
Message text is too long
No message text provided
Too many attachments were provided with this message. A maximum of 100 attachments are allowed on a message.
Intended recipient is not in the specified channel.
No authentication token provided.
Invalid authentication token.
Authentication token is for a deleted user or workspace.
The workspace token used in this request does not have the permissions necessary to complete the request.
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). 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-8iso-8859-1.
The method was called via a POST request with Content-Typeapplication/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-urlencodedmultipart/form-datatext/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.
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.