In my experience, IE6-8 can handle UTF-8 filenames if (1) the extension is alphanumeric; (2) you percent-encode the rest of the filename, making sure that whitespace is encoded as "%20" rather than "+"; and (3) you put the whole thing between double quotes. Use RFC2231 for all other browsers, although slightly older versions of Chrome and Safari might cause trouble from time to time.
But nowadays I'm so comfortable with just using the URL that the above encoding schemes just feel like unnecessary hassle. HTTP was designed to display the filename in plain sight in the URL, not bury it in a header. Use it as intended and even IE will happily comply.
But nowadays I'm so comfortable with just using the URL that the above encoding schemes just feel like unnecessary hassle. HTTP was designed to display the filename in plain sight in the URL, not bury it in a header. Use it as intended and even IE will happily comply.