Since we're on the subject, a couple points to share...
1. If you're delivering unique objects based on the User-Agent, make
sure that you either mark the content no-cache, or make sure that each
different object has a unique ETag. IIRC, Adding Vary: User-Agent is
mandatory as well if you're expecting the object to be cached, except
that that creates a big potential failure case I'll illustrate below.
A far better idea is to issue a 301 Redirect to user-agent-specific
sites (mobile.site.com, for example), or use javascript to branch on
navigator.userAgent to avoid having to serve unique objects for
different UAs in the first place. Option #2 may be impossible due to
object size reasons (I know flickr wasn't able to do it, they had to
use the 301 option to send a mobile-specific .js and .css), so pick
what works best for you.
2. If you are behind a squid reverse proxy with broken_vary_encoding
turned on (often necessary, thanks apache and lighttpd), do NOT send
Vary: User-Agent from the origin on a cacheable object. You will wind
up with a unique object in the cache for every unique variation of the
client User-Agent string (which, in my horror-story example, numbered
in the tens of thousands for a moderately popular site). Not a
pleasant tale to tell.
HTH,
-Chris
On Jun 16, 2009, at 11:21 PM, Amos Jeffries wrote:
On Tue, 16 Jun 2009 08:05:17 +0200, Luis Daniel Lucio Quiroz
<luis.daniel.lucio@xxxxxxxxx> wrote:
Hi Squids,
How do you think should be the best way to detect if a user is
surfing
inet
throut its mobile/handset?
TIA
LD
Pretty much the purpose of the User-Agent: header.
Amos
