Hey Community!
I’m trying to upload files directly to Slack using the HTTP Request node in n8n.
I cannot use the built-in Slack node because I need to dynamically use different auth tokens per workflow/client — so I need a flexible, credential-agnostic solution.
What I’m trying to do
The Slack API provides me with an upload_url and instructs to upload (POST) a file to this URL, just like this cURL command:
curl -X POST -T "myfile.jpg" -H "Content-Type: application/octet-stream" "https://files.slack.com/upload/v1/XXXXXXXX..."
This works perfectly and returns a 200 from Slack (or an empty HTML, as expected).
The problem
When I try to do the same upload using the HTTP Request node in n8n (I’ve tried all available Body Content Types: RAW, File, Form-Data), I always get an HTML response from Slack (looks like a generic web page, not a proper API response).
It seems like the file is not being uploaded in the exact same way as curl does (pure binary data, no multipart, no field).
I also tried to manually convert the file to a buffer from a base64 string, but then it uploaded the whole byte array (not the real binary).
My main question
How can I replicate this exact cURL behavior in n8n using the HTTP Request node? Specifically, how can I POST a file as plain binary data (no multipart, no encoding, no JSON), with a custom Content-Type, to a URL that changes dynamically?
Extra details:
-
The file is present in the binary section of the input item (
binary.data). -
The upload works with curl, but with n8n I only get HTML responses, never the expected result or a success.
Any examples, screenshots or working configurations for n8n v1.93+ would be greatly appreciated!
Thanks!