Flickr Sends Goofy HTTP Headers
Note to archeologists and readers: this was written a long time ago and is maintained simply for historical reasons.
Flickr is sending the following HTTP headers when I request an image from their site:
<http://static.flickr.com/25/45701618_b33d84770b_s.jpg>GET /25/45701618_b33d84770b_s.jpg HTTP/1.1
Host: static.flickr.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.10) Gecko/20050716 Firefox/1.0.6
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: cookie_epass=9df5184c71b811e5bf1081de83e24d51; cookie_accid=16665; cookie_session=16665%3A9df5184c71b811e5bf1081de83e24d51; use_master_until=1127567132
Pragma: no-cache
Cache-Control: no-cache
HTTP/1.x 200 OK
Date: Fri, 23 Sep 2005 01:13:26 GMT
Server: Apache/2.0.52 (Red Hat)
Last-Modified: Fri, 23 Sep 2005 01:13:23 GMT
Etag: “91e011-d08-1dacd2c0”
Accept-Ranges: bytes
Content-Length: 3336
Content-Type: image/jpeg
X-Cache: HIT from storage7.flickr.mud.yahoo.com
Connection: close
This is completely valid HTTP, but I really wish they were sending back a proper Expires header like this:
Expires: Mon, 24 Oct 2005 15:12:45 GMT
If they sent back this HTTP header, my browser wouldn’t have to perform conditional-GET requests for subsequent loads of images on Flickr. The part of the HTTP request that makes the GET conditional is highlighted below:
`GET /25/45701618_b33d84770b_s.jpg HTTP/1.1
Host: static.flickr.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.10) Gecko/20050716 Firefox/1.0.6
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,/;q=0.5
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
Cookie: cookie_epass=9df5184c71b811e5bf1081de83e24d51; cookie_accid=16665; cookie_session=16665%3A9df5184c71b811e5bf1081de83e24d51; use_master_until=1127567132
If-Modified-Since: Fri, 23 Sep 2005 01:13:23 GMT
If-None-Match: “91e011-d08-1dacd2c0”
Cache-Control: max-age=0`
HTTP/1.x 304 Not Modified
Date: Sat, 24 Sep 2005 15:19:32 GMT
Server: Apache/2.0.52 (Red Hat)
Etag: “91e011-d08-1dacd2c0”
X-Cache: MISS from storage7.flickr.mud.yahoo.com
Connection: close
Instead, my browser would notice that it has been told not to request this resource until Oct 24th, which is exactly one month from today and would display th e image from the local browser cache. There wouldn’t be any network overhead at all and Flickr images would be served a lot faster.
I don’t see what the point of only allowing conditional GET requests is. Flickr isn’t benefitting anybody by doing this. Failing to use Expires: headers for static content only serves to slow down the user experience and increase load on their systems.
Sysadmins at Flickr: read the mod_expires documentation and switch this thing on.