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Uploads or creates a file.


Method URL:
Preferred HTTP method: POST
Accepted content types: multipart/form-data, application/x-www-form-urlencoded
Rate limiting: Tier 2
Works with:
Token type Required scope(s)
bot bot
user files:write:user

File threads are here

A new file commenting experience arrived on July 23, 2018. Learn more about what's new and the migration path for apps already working with files and file comments.

This method allows you to create or upload an existing file.


Argument Example Required Description
token xxxx-xxxxxxxxx-xxxx Required

Authentication token bearing required scopes.

channels C1234567890,C2345678901,C3456789012 Optional

Comma-separated list of channel names or IDs where the file will be shared.

content ... Optional

File contents via a POST variable. If omitting this parameter, you must provide a file.

file ... Optional

File contents via multipart/form-data. If omitting this parameter, you must submit content.

filename foo.txt Optional

Filename of file.

filetype php Optional

A file type identifier.

initial_comment Best! Optional

The message text introducing the file in specified channels.

thread_ts 1234567890.123456 Optional

Provide another message's ts value to upload this file as a reply. Never use a reply's ts value; use its parent instead.

title My File Optional

Title of file.

Present arguments as parameters in application/x-www-form-urlencoded querystring or POST body. This method does not currently accept application/json.

You must provide either a file or content parameter.

The content of the file can either be posted using an enctype of multipart/form-data (with the file parameter named file), in the usual way that files are uploaded via the browser, or the content of the file can be sent as a POST var called content. The latter should be used for creating a "file" from a long message/paste and forces "editable" mode.

In both cases, the type of data in the file will be intuited from the filename and the magic bytes in the file, for supported formats.

Sending a valid filetype parameter will override this behavior. Possible filetype values can be found in the file object definition.

Files uploaded via multipart/form-data will be stored either in hosted or editable mode, based on certain heuristics (determined type, file size).

The file can also be shared directly into channels on upload, by specifying an optional argument channels. If there's more than one channel name or ID in the channels string, they should be comma-separated.

There is a 1 megabyte file size limit for files uploaded as snippets.

Upload files and images into message threads by providing the thread parent's ts value with the thread_ts parameter.

The initial_comment field is used in messages to introduce the file in conversation.


By default all newly-uploaded files are private and only visible to the owner. They become public once they are shared into a public channel (which can happen at upload time via the channels argument).

If successful, the response will include a file object.

Success response after uploading a file to a channel with an initial message

    "ok": true,
    "file": {
        "id": "F0TD00400",
        "created": 1532293501,
        "timestamp": 1532293501,
        "name": "dramacat.gif",
        "title": "dramacat",
        "mimetype": "image/jpeg",
        "filetype": "gif",
        "pretty_type": "JPEG",
        "user": "U0L4B9NSU",
        "editable": false,
        "size": 43518,
        "mode": "hosted",
        "is_external": false,
        "external_type": "",
        "is_public": false,
        "public_url_shared": false,
        "display_as_bot": false,
        "username": "",
        "url_private": "https://.../dramacat.gif",
        "url_private_download": "https://.../dramacat.gif",
        "thumb_64": "https://.../dramacat_64.gif",
        "thumb_80": "https://.../dramacat_80.gif",
        "thumb_360": "https://.../dramacat_360.gif",
        "thumb_360_w": 360,
        "thumb_360_h": 250,
        "thumb_480": "https://.../dramacat_480.gif",
        "thumb_480_w": 480,
        "thumb_480_h": 334,
        "thumb_160": "https://.../dramacat_160.gif",
        "image_exif_rotation": 1,
        "original_w": 526,
        "original_h": 366,
        "permalink": "https://.../dramacat.gif",
        "permalink_public": "https://.../More-Path-Components",
        "comments_count": 0,
        "is_starred": false,
        "shares": {
            "private": {
                "D0L4B9P0Q": [
                        "reply_users": [],
                        "reply_users_count": 0,
                        "reply_count": 0,
                        "ts": "1532293503.000001"
        "channels": [],
        "groups": [],
        "ims": [
        "has_rich_preview": false

Uploading a file with the content parameter creates an editable text/plain file by default

    "ok": true,
    "file": {
        "id": "F0TD0GUTS",
        "created": 1532294750,
        "timestamp": 1532294750,
        "name": "-.txt",
        "title": "Untitled",
        "mimetype": "text/plain",
        "filetype": "text",
        "pretty_type": "Plain Text",
        "user": "U0L4B9NSU",
        "editable": true,
        "size": 11,
        "mode": "snippet",
        "is_external": false,
        "external_type": "",
        "is_public": true,
        "public_url_shared": false,
        "display_as_bot": false,
        "username": "",
        "url_private": "https://.../.txt",
        "url_private_download": "",
        "permalink": "https://.../.txt",
        "permalink_public": "https://.../.txt",
        "edit_link": "https://.../.txt/edit",
        "preview": "launch plan",
        "preview_highlight": "<div class=\"CodeMirror cm-s-default CodeMirrorServer\" oncopy=\"if(event.clipboardData){event.clipboardData.setData('text/plain',window.getSelection().toString().replace(/\\u200b/g,''));event.preventDefault();event.stopPropagation();}\">\n<div class=\"CodeMirror-code\">\n<div><pre>launch plan</pre></div>\n</div>\n</div>\n",
        "lines": 1,
        "lines_more": 0,
        "preview_is_truncated": false,
        "comments_count": 0,
        "is_starred": false,
        "shares": {
            "public": {
                "C061EG9SL": [
                        "reply_users": [],
                        "reply_users_count": 0,
                        "reply_count": 0,
                        "ts": "1532294750.000001",
                        "channel_name": "general",
                        "team_id": "T061EG9R6"
        "channels": [
        "groups": [],
        "ims": [],
        "has_rich_preview": false

Typical error response

    "ok": false,
    "error": "invalid_auth"


Upload "dramacat.gif" from the current directory and share it in two channels, using multipart/form-data:

curl -F file=@dramacat.gif -F "initial_comment=Shakes the cat" -F channels=C024BE91L,D032AC32T -H "Authorization: Bearer xoxa-xxxxxxxxx-xxxx"

Create an editable text file containing the text "launch plan":

curl -F "content=launch plan" -H "Authorization: Bearer xoxb-xxxxxxxxx-xxxx"

Upload another image to an existing message thread:

curl -F file=@drworm.gif -F "initial_comment=I play the drums." -F channels=C024BE91L -F thread_ts=1532293503.000001 -H "Authorization: Bearer xoxp-xxxxxxxxx-xxxx"


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

An admin has restricted posting to the #general channel.


One or more channels supplied are invalid


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.


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.