When you are in Data Publish, Target-> Entity and you define the file, Qlik doesn't assign an extension, i.e., csv or txt, etc. After you have provided a Entity file format, i.e., TEXTFILE and Field Delimiter, i.e., comma, Qlik still stores the output file in AWS S3 bucket without an extension. In this example, it would be .csv. To be able to open the file, you need to manually download it to your desktop and add an extension. This manual work is not efficient.