You can change what action Firefox takes for defined content types. When you tell Firefox to open or save the file and also check the option to 'Do this automatically for files like this from now on' ( see below), a new Content Type and Action entry for that type of file will appear in the Applications section of the General panel in Firefox Options Preferences Settings (If you decide to use an add-on and you need help with it, you should visit the add-on site or contact the add-on developer directly for support.) (To learn more, see Properly configuring server MIME types at MDN web docs.) You can contact the website in such cases or you can try a Firefox add-on such as Content-Type Fixer to work around the problem. For example, Firefox may display the content as plain text instead of opening the file in an application or asking you what to do. Note: Firefox will not be able to properly handle a file download if a misconfigured web server sends it with an incorrect Content type.