Possible Values: true/false
When not specified or set to 'falsetrue', any existing files will not be overwritten by the file upload widget. If any of the file names being uploaded already exist in the target directory, a validation error message will display next to the file upload widget and . When set to 'false' no files will be uploaded.When overwritten. If "generate unique names" is set to ' true', any file names already existing in the target directory will be overwritten by the uploaded files, then the files will be saved with automatically generated unique names. Otherwise, an error will be returned when files already exist.