Argument	Type	Description
`token`Required	token	Authentication token bearing required scopes. Tokens should be passed as an HTTP Authorization header or alternatively, as a POST parameter. Example`xxxx-xxxxxxxxx-xxxx`
`channel`Required	string	Channel, private group, or IM channel to send message to. Can be an encoded ID, or a name. Example`C1234567890`
`text`Required		How this field works and whether it is required depends on other fields you use in your API call. See below for more detail. Example`Hello world`
`user`Required	string	`id` of the user who will receive the ephemeral message. The user should be in the channel specified by the `channel` argument. Example`U0BPQUNTA`
`as_user`	boolean	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. Example`true`
`attachments`		A JSON-based array of structured attachments, presented as a URL-encoded string. Example`[{"pretext": "pre-hello", "text": "text-world"}]`
`blocks`	blocks[]	A JSON-based array of structured blocks, presented as a URL-encoded string. Example`[{"type": "section", "text": {"type": "plain_text", "text": "Hello world"}}]`
`icon_emoji`	string	Emoji to use as the icon for this message. Overrides `icon_url`. Must be used in conjunction with `as_user` set to `false`, otherwise ignored. See authorship below. Example`:chart_with_upwards_trend:`
`icon_url`	string	URL to an image to use as the icon for this message. Must be used in conjunction with `as_user` set to false, otherwise ignored. See authorship below. Example`http://lorempixel.com/48/48`
`link_names`	boolean	Find and link channel names and usernames. Example`true`
`parse`		Change how messages are treated. Defaults to `none`. See below. Example`full`
`thread_ts`		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. Example`1234567890.123456`
`username`	string	Set your bot's user name. Must be used in conjunction with `as_user` set to false, otherwise ignored. See authorship below. Example`My Bot`

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

Example responses

Common successful response

Typical success response

{
    "ok": true,
    "message_ts": "1502210682.580145"
}

Common error response

Typical error response

{
    "ok": false,
    "error": "user_not_in_channel"
}

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.

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.

Formatting

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.

Authorship

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.

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.

Errors

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
`restricted_action`	A workspace preference prevents the authenticated user from posting.
`too_many_attachments`	Too many attachments were provided with this message. A maximum of 100 attachments are allowed on a message.
`is_archived`	Channel has been archived.
`channel_not_found`	Value passed for `channel` was invalid.
`msg_too_long`	Message text is too long
`no_text`	No message text provided
`user_not_in_channel`	Intended recipient is not in the specified channel.
`not_authed`	No authentication token provided.
`invalid_auth`	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.
`account_inactive`	Authentication token is for a deleted user or workspace when using a `bot` token.
`token_revoked`	Authentication token is for a deleted user or workspace or the app has been removed when using a `user` token.
`no_permission`	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.
`org_login_required`	The workspace is undergoing an enterprise migration and will not be available until migration is complete.
`ekm_access_denied`	Administrators have suspended the ability to post a message.
`missing_scope`	The token used is not granted the specific scope permissions required to complete this request.
`not_allowed_token_type`	The token type used in this request is not allowed.
`method_deprecated`	The method has been deprecated.
`deprecated_endpoint`	The endpoint has been deprecated.
`two_factor_setup_required`	Two factor setup is required.
`enterprise_is_restricted`	The method cannot be called from an Enterprise.
`team_access_not_granted`	The token used is not granted the specific workspace access required to complete this request.
`invalid_arguments`	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.
`invalid_arg_name`	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.
`invalid_array_arg`	The method was passed an array as an argument. Please only input valid strings.
`invalid_charset`	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`.
`invalid_form_data`	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.
`invalid_post_type`	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`.
`missing_post_type`	The method was called via a `POST` request and included a data payload, but the request did not include a `Content-Type` header.
`team_added_to_org`	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.
`invalid_json` [hidden]	The method was called via a `POST` request with `Content-Type` `application/json`, but the body was not valid JSON.
`json_not_object` [hidden]	The method was called via a `POST` request a valid JSON body, but the JSON value was not an object.
`ratelimited`	The request has been ratelimited. Refer to the `Retry-After` header for when to retry the request.
`accesslimited`	Access to this method is limited on the current network
`request_timeout`	The method was called via a `POST` request, but the `POST` data was either missing or truncated.
`upgrade_required` [hidden]	The calling application needs to be upgraded.
`service_unavailable`	The service is temporarily unavailable
`fatal_error`	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.
`internal_error`	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.

Warnings

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
`missing_charset`	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.
`superfluous_charset`	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.

API response

URL

POST body

Submit your arguments to see the API response

Calling chat.postEphemeral

Java

JavaScript

Java

import com.slack.api.bolt.App;
import com.slack.api.bolt.AppConfig;
import com.slack.api.bolt.jetty.SlackAppServer;
import com.slack.api.methods.SlackApiException;

import java.io.IOException;

public class ChatPostEphemeral {

    public static void main(String[] args) throws Exception {
        var config = new AppConfig();
        config.setSingleTeamBotToken(System.getenv("SLACK_BOT_TOKEN"));
        config.setSigningSecret(System.getenv("SLACK_SIGNING_SECRET"));
        var app = new App(config); // `new App()` does the same

        app.message("secret", (req, ctx) -> {
            var logger = ctx.logger;
            try {
                var event = req.getEvent();
                // Call the chat.postEphemeral method using the built-in WebClient
                var result = ctx.client().chatPostEphemeral(r -> r
                    // The token you used to initialize your app is stored in the `context` object
                    .token(ctx.getBotToken())
                    // Payload message should be posted in the channel where original message was heard
                    .channel(event.getChannel())
                    // The user the message should appear for
                    .user(event.getUser())
                    .text("Shhhh only you can see this :shushing_face:")
                );
                logger.info("result: {}", result);
            } catch (IOException | SlackApiException e) {
                logger.error("error: {}", e.getMessage(), e);
            }
            return ctx.ack();
        });

        var server = new SlackAppServer(app);
        server.start();
    }
}

JavaScript

Code to initialize Bolt app
// Require the Node Slack SDK package (github.com/slackapi/node-slack-sdk)
const { WebClient, LogLevel } = require("@slack/web-api");

// WebClient insantiates a client that can call API methods
// When using Bolt, you can use either `app.client` or the `client` passed to listeners.
const client = new WebClient("xoxb-your-token", {
  // LogLevel can be imported and used to make debugging simpler
  logLevel: LogLevel.DEBUG
});
// ID of the channel you want to send the message to
const channelId = "C12345";
// ID of the user you want to show the ephemeral message to
const userId = "U12345";

try {
  // Call the chat.postEphemeral method using the WebClient
  const result = await client.chat.postEphemeral({
    channel: channelId,
    user: userId,
    text: "Shhhh only you can see this :shushing_face:"
  });

  console.log(result);
}
catch (error) {
  console.error(error);
}

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chat.postEphemeral

Facts

Method access

Required scopes

Content types

Rate limits

Arguments