[danielbln]

Usually it's a HTTP header that's sent to your browser: Content-Disposition: attachment

[est31]

Or content-disposition as of HTTP/2. Just verified with the browser console that it's sending that header (and using HTTP/2).

[_ph_]

Thanks, I had always wondered why some sites behave differently with some file types. A bit annoying, if you just want to glance at something for a while but not keep it around for longer.

[danielbln]

There are browser addons that force the browser to ignore this header, for chrome e.g. https://chrome.google.com/webstore/search/undisposition?hl=e....