Why Does Sending a PDF Binary from an n8n Form Node to a Workflow Fail with a Missing Binary Error?

Below is a possible explanation and some troubleshooting steps:

What’s Happening

The error

This operation expects the node’s input data to contain a binary file ‘PDF’, but none was found [item 0]
Make sure that the previous node outputs a binary file

indicates that the node downstream expects the full binary data for PDF – not just the metadata such as filename, mimetype, and size. In your output, the PDF property only contains metadata. For binary operations, n8n expects an actual binary property (typically a “data” field containing the file buffer encoded in base64).

Why This Might Be Occurring

• File Not Fully Transferred: The Form node might now only output the file’s metadata instead of both metadata and the actual binary content. This change might result from a misconfiguration or an update in how the file is processed.
• Configuration or Environment Changes: When working with binary data, especially in self-hosted or containerized environments, configuration (for example, setting up the binary data storage mode) is important. If any settings changed in your Railway deployment (or environment variables were updated), that could affect whether the binary data is being preserved and passed on.

Troubleshooting Steps

1. Check the Form Node Configuration:
   Verify if there are any recent changes in the way the form node processes file uploads. Make sure it is configured to output the complete binary data (i.e., metadata plus the actual data buffer).

2. Inspect Binary Data Output:
   Test your workflow and inspect the complete output from the form node. You should see a property under your PDF object (typically named data) that holds the base64 encoded string of the file’s contents. For example, a correct output would look like:

   JSONCopied
   {
     "PDF": {
       "data": "base64EncodedFileData...",
       "filename": "KNECKES-Heures-test.pdf",
       "mimetype": "application/pdf",
       "size": 74834
     },
     "submittedAt": "2025-01-17T11:13:14.207+01:00",
     "formMode": "production"
   }

   If the data property is missing, that confirms the file buffer isn’t being passed along.

3. Review Environment Variables:
   If you run n8n on Railway or any containerized setup, ensure that binary data mode settings are correctly configured. There are several environment variables available (such as those controlling the binary data storage path) that can affect binary data handling. If these were modified or if your deployment recently updated its configuration, restoring or adjusting those variables might resolve the issue.

4. Double-Check Workflow Wiring:
   Ensure that the workflow wiring passes the correct data from the form node to the subsequent node expecting the PDF binary data.

Next Steps

• Confirm that your file upload node is correctly capturing both the metadata and the file buffer.
• Investigate any changes in your environment (Railway deployment, environment variables, etc.) around the time the workflow started failing.
• If you recently updated n8n or any related plugins, check the changelogs for any modifications related to binary data handling.

By following these steps, you should be able to pinpoint whether the loss of actual binary data (the encoded file buffer) is due to configuration, changes in node behavior, or environment settings.