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.
If successful, the response will include a file object.
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).
Upload "dramacat.gif" and share it in channel, using multipart/form-data:
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.
An admin has restricted posting to the #general channel.
One or more channels supplied are invalid
No authentication token provided.
Invalid authentication token.
Authentication token is for a deleted user or workspace.
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.