Issue with Audio File Upload to AssemblyAI API in n8n

[Lucas_P]

Hello,

I’m encountering an issue while trying to upload an audio file to the AssemblyAI API via n8n. I keep receiving a 422 error with the following message:

“Upload failed, please try again. If you continue to have issues please reach out to support”

Here are the details of my setup:

• Method: POST
• API URL: https://api.assemblyai.com/v2/upload
• Authorization Header: Correct API key
• Content-Type: application/octet-stream
• Data Sent: I’m passing the raw binary data of a .m4a file via {{$binary.audio.data}} from a form submission (file size: ~18MB, type: audio/x-m4a)
• Issue: The upload consistently fails with a 422 error, even when mimicking the curl --data-binary request from the AssemblyAI documentation.

What I’ve Tried:

• Sending the file as binary (file set as binary type in n8n), but this results in a timeout.
• Testing with a smaller file to check if the issue is related to the file size, but the error still persists.
• Double-checking the API key and file type, which seem correct.

Question:

Has anyone encountered this error when uploading files to AssemblyAI via n8n? Are there any specific settings or parameters I should adjust to make the upload work?

Thanks in advance for any suggestions or advice!
Lucas

[interss]

Hello @Lucas_P

See if this solution makes sense for you

The Content-Type header is incorrect for uploading binary files

Adjust the HTTP Request Node
Select the “Upload Audio” node

Set the following parameters below;

Method: POST
URL: api.assemblyai.com
Authentication: Header Auth

Headers:
Name: authorization
Value: YOUR_API_KEY
Name: Content-Type
Value: application/octet-stream (IMPORTANT: do not use multipart/form-data)

Request Content: Binary
Binary Data: {{$binary.audio.data}}

Options:
Timeout: 120000 (increase to 120 seconds due to file size)
Ignore Response Code: Disabled

Form Trigger node keep the current setting, just make sure the field is set to “file” type
The “multipleFiles” option is set to false

Content-Type: The AssemblyAI API expects application/octet-stream for direct binary uploads, not multipart/form-data

Binary Data: Send the binary data directly in the body of the request request, not as a form parameter

Timeout: Increase the timeout for large files (18MB may take longer to upload)

File Format: Make sure the .m4a file is not corrupted by testing it in another player

Suggest your stream with some fixes

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