ConvertAPI giving 4000 Parameter validation error - file must be greater than 0, but I'm sending a large file

I'm trying to post to ConvertAPI's pdf/to/jpg endpoint, and am getting the following error:

 {"Code":4000,"Message":"Parameter validation error.","InvalidParameters":{"File":["File size must be greater than 0 bytes.","The File field is required."]}}

I am sending the file data, which I receive as a blob and base64encode, and can see it in my debugs.

My request, with the base64 string truncated:


Does anyone have any idea what I'm getting wrong?


  • The request JSON payload is not correct. You can find the correct one at

        "Parameters": [
                "Name": "File",
                "FileValue": {
                    "Name": "my_file.pdf",
                    "Data": "<Base64 encoded file content>"

    Also I suggest to use multipart for requests and not JSON.