The URL is served as application/octet-stream and not as application/pdf. That alone would be enough to force a file save as but the site serves this file also with a "content-disposition: attachment" header with always forces a save as window.
HTTP/1.0 200 OK Content-Type: application/octet-stream; charset=UTF-8 Cache-Control: max-age=1, must-revalidate Date: Wed, 10 Dec 2014 23:56:05 GMT Last-Modified: Wed, 04 Nov 2009 22:07:14 GMT ETag: "1257372434539" Content-Length: 3964021 content-disposition: attachment; filename="benny2008-Lodamin-NEWS.pdf" X-Content-Type-Options: nosniff X-Frame-Options: SAMEORIGIN X-XSS-Protection: 1; mode=block Server: GSE Alternate-Protocol: 443:quic,p=0.02 Connection: Keep-Alive -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1400982 Title: PDF Preview in Firefox not honored for specific URL To manage notifications about this bug go to: https://bugs.launchpad.net/firefox/+bug/1400982/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs