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Adds a reaction to an item.


Method URL: https://slack.com/api/reactions.add
Preferred HTTP method: POST
Accepted content types: application/x-www-form-urlencoded, application/json
Works with:
Token type Required scope(s)
bot bot
workspace reactions:write
user reactions:write post

This method adds a reaction (emoji) to an item (file, file comment, channel message, group message, or direct message). One of file, file_comment, or the combination of channel and timestamp must be specified.


Argument Example Required Description
token xxxx-xxxxxxxxx-xxxx Required

Authentication token bearing required scopes.

name thumbsup Required

Reaction (emoji) name.

channel C1234567890 Optional

Channel where the message to add reaction to was posted.

file F1234567890 Optional

File to add reaction to.

file_comment Fc1234567890 Optional

File comment to add reaction to.

timestamp 1234567890.123456 Optional

Timestamp of the message to add reaction to.

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


Typical success response

    "ok": true

Typical error response

    "error": "already_reacted",
    "ok": false

After making this call, the reaction is saved and a reaction_added event is broadcast through the RTM API for the calling 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.

Error Description

Value passed for timestamp was invalid.


File specified by file does not exist.


File comment specified by file_comment does not exist.


Message specified by channel and timestamp does not exist.


file, file_comment, or combination of channel and timestamp was not specified.


Value passed for name was invalid.


The specified item already has the user/reaction combination.


The limit for distinct reactions (i.e emoji) on the item has been reached.


The limit for reactions a person may add to the item has been reached.


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.


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[7]). 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-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/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.

Warning Description

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.