From Xojo Documentation
When True, the browser will always download the file rather than try to display it. For example, most web browsers will try to display simple text files and many will display PDF files inline. Set ForceDownload to True to instead ensure these types of files are downloaded instead.
Create a new file for downloading:
TextFile.MimeType = "text/plain"
TextFile.ForceDownload = True // If False, the browser may try to display the file instead of download it
TextFile.FileName = "TextFile.txt"
TextFile.Data = "Hello, world!"
ShowURL(TextFile.URL) // This causes the file to be downloaded