Firefox adds an action if you tick the box in the download dialog to do this automatically and this choice is only available if the website send the file as a valid MIME type for this file extension and not with a generic type like "application/octet-stream" or "content-disposition:attachment".

• https://support.mozilla.org/en-US/kb/change-firefox-behavior-when-open-file

Thank you for your reply.

The 2 file types I most frequently encounter for which the "do this from now on" check box is not offered are RAR (WinRAR Compressed Archive) and WMV (Windows Media [Video]). Browsing through your attached link, I found in FILExt that there is a valid MIME type registered for both of these. So the reason the check box is not offered for these file types appears to be (A) the [multiple] servers from which these files are requested are not correctly reporting the MIME type, or (B) these MIME types are not registered in Firefox. Please tell me whether, or how to determine if (B) is true and if so, what further action I need to take to get it corrected.

Yours truly, Mark Spears (buben8r)