Add extension .csv to file created with Views Data Export
In the view settings click on Format: CSV File &gt; Settings



In the dialog box that appear, be sure that Provide as file is selected. In the Filename field that appears when that option is selected, leave the default value (%view.csv).



%view, which adds the view machine name to the filename, is only one of the available replacement tokens. As visible in the screenshot, the other ones are:

%display
%exposed
%timestamp-full
%timestamp-yy
%timestamp-yyyy
%timestamp-mm
%timestamp-mmm
%timestamp-dd
%timestamp-ddd
%timestamp-hh
%timestamp-ii
%timestamp-ss