How can I change the binary MIME type to video/mp4 in n8n for WhatsApp Business Cloud?

Below is one workaround that has worked for others. Since you can’t change the MIME type directly through Set or Edit Fields nodes, you can add a Function node to override the binary property’s MIME type before passing it to the WhatsApp node.

For example, insert a Function node between where you receive the file and the WhatsApp upload node and use code like this:

JAVASCRIPTCopied
// Loop through all items (usually one)
items.forEach(item => {
  // Check if the binary property exists and contains the file data,
  // here "data" is the key for the binary property – adjust if yours is different.
  if (item.binary && item.binary.data) {
    // Overwrite the MIME type:
    item.binary.data.mimeType = 'video/mp4';
  }
});
return items;

How It Works

• The Function node iterates over the items.
• It checks for the binary property (in this example, the key is “data” – if yours differs update it accordingly) and then sets its mimeType field to "video/mp4".
• This modified binary output is then passed onto the WhatsApp node, which should now receive the file with the correct MIME type.

Make sure in the WhatsApp Business Cloud node you’re setting the Input Data Field Name to the field name (in this case, data) rather than an expression. This ensures the node uses the binary data as provided.

Using this workaround should allow you to successfully upload your MP4 file without WhatsApp rejecting it due to the MIME type.