An error occurred while creating features. (Duplicate field names are not allowed. ())

Error Message

Attempting to add a CSV file to a web map in ArcGIS Online Map Viewer fails, and returns the following error message:

Error: An error occurred while creating features. (Duplicate field names are not allowed. ())

Cause

The error may occur when the table contains a column without a header.

Solution or Workaround

To solve the issue, insert values for the blank column header field.

1. Open the CSV file in Microsoft Excel.
2. Specify values for the blank column header. In the following example, the blank column header is named Pinpoint.

3. Save the CSV file.
4. Add the file to ArcGIS Online Map Viewer. Refer to ArcGIS Online: Add layers from files for step to do this.