Why Are Excel/CSV Uploads Failing in My n8n Form Trigger Workflow?

Below is some guidance based on common troubleshooting steps for file upload issues with the Form Trigger:

What’s Happening

When you submit an Excel or CSV file, you see the error:

  “Problem submitting response
  Please try again or contact support if the problem persists”

Meanwhile, uploads with other file types (e.g. pdf, docx, png) work as expected.

Potential Causes

• MIME Type / Encoding Issues:
  The form trigger may be handling file uploads based on MIME type. Excel or CSV files might be sent with headers or encoding that the node isn’t expecting.

• File Size or Data Handling:
  Sometimes, binary data for certain file types may be affected by size limits or how the node processes the incoming multipart data.

• Configuration or Reverse Proxy:
  If you’re running n8n in Docker (self-hosted), it’s worth checking that any reverse proxy or web server sitting in front of n8n isn’t altering the request (or its content type) for Excel/CSV files.

Troubleshooting Steps

1. Inspect Request and Headers:
   Use developer tools in your browser (or a tool like Postman) to check which headers and content types are being sent with your Excel or CSV file. Compare these with those sent when a supported file type (pdf, for example) is uploaded.

2. Examine n8n Logs:
   Check the container’s logs for more details on what is happening when the file is submitted. Run:

   SHCopied
   docker logs [CONTAINER_ID]

   Look for any errors or warnings around file processing.

3. Test with a Minimal Workflow:
   Create a simple workflow using the Form Trigger that solely attempts to capture and output the file data. This can help you narrow down whether it’s the form trigger itself or further processing that causes the failure.

4. Review Your Reverse Proxy/Network Settings:
   If you are running n8n behind a proxy (or if Docker is forwarding ports), check that nothing in your network setup is interfering with larger or differently encoded file uploads.

Next Steps

• Based on your Enterprise subscription:
  If these steps don’t help resolve the issue, providing detailed logs and header information to n8n support might uncover if there’s a bug or configuration nuance with handling these file types.

• Community Discussion:
  Also consider checking the n8n community forums or documentation updates, as file handling issues are sometimes subject to changes in how binary data is processed.

Following these steps should help isolate whether the issue is with the file itself, the Form Trigger’s handling of that file type, or an external factor in your deployment setup.

Based on the information provided, one possibility is that the file field used in your form trigger (or subsequent n8n Form node) is not configured to accept Excel/CSV file types. In the n8n documentation for the Form node, file fields can have an option called acceptFileTypes where you specify which file extensions are allowed. For example:

JSONCopied
{
	"fieldLabel": "Upload File",
	"fieldType": "file",
	"multipleFiles": false,
	"acceptFileTypes": ".csv, .xls, .xlsx, .pdf, .docx, .png"
}

If your file field does not include Excel or CSV extensions (or if it uses a default allowing only a subset of file types), then uploads of those files could be rejected with a generic error message such as:

  “Problem submitting response
   Please try again or contact support if the problem persists”

A few steps to troubleshoot and resolve this:

1. Check Your Form Field Configuration:
   Ensure that the field that accepts uploads explicitly allows Excel and CSV file types by setting the acceptFileTypes to include extensions like .csv, .xls, or .xlsx.

2. Review Client-side Validation:
   If your form (or the Form node configuration) performs client- or server-side validation on the file type, verify that Excel/CSV are not being incorrectly rejected.

3. Test the Form Using the Test URL:
   Use the test URL provided by the Form Trigger node to see detailed errors in the editor UI. This may offer clues on why the upload isn’t accepted.

4. Confirm File Size and Memory Limitations:
   Although your issue seems to be related to file type, it’s also a good idea to check that the size of the Excel/CSV files isn’t triggering any memory or processing limits on your self-hosted setup.

Since other file types like PDF, DOCX, or PNG work correctly, the most likely culprit is the configuration around file type acceptance. Reviewing and updating your form’s configuration (or the JSON definition if you’re defining it with JSON) should help resolve the issue.

If after these changes the issue persists, consider checking the network response in your browser’s developer tools as well as the n8n server logs, as they may provide more detailed error information.