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From Tom Evans <tevans...@googlemail.com>
Subject Re: [users@httpd] Browser, Apache and caching...
Date Wed, 02 Feb 2011 17:47:41 GMT
On Wed, Feb 2, 2011 at 5:06 PM, Tony Anecito <adanecito@yahoo.com> wrote:
> Hi All,
>
> I am wondering for the browser cache to work does the expires headers in the
> apache config file have to be setup? Or by default when the page request from
> the browser hits apache does it look at the file modified time stamp for the
> file on disk or Apache cache and compares to whatever the request has in it (I
> assume a file timestamp)?
>
> Just trying to figure out if expires header is really needed because if you use
> it by setting a future date then the only way to get the file sent across due to
> some change is to rename it slightly.
>
> Thanks,
> -Tony
>

Correct, sending an Expires header will make UA caches store the
object unconditionally until it gets ejected or the date specified is
reached.

Instead of sending Expires, if you send a Last-Modified header (which
will happen by default for files served from disk by Apache), then the
next time the UA requests that, it should add a header
If-Modified-Since header. If the file hasn't been modified since that
time, then Apache will send an empty 304 response (Not Modified), and
the UA will serve from cache.

Cheers

Tom

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