Posted by Michael Winter on 03/08/06 17:30

On 08/03/2006 11:51, Jim Higson wrote:

[snip]

> Because the resource for a given URL never changes, browser cache is
> always safe to use and there is no need to revalidate. What are the
> best HTTP header(s) to use to indicate this, and how should they be
> set in Apache?

There is no specific method with to mark a resources as indefinitely
'fresh'. However, one can get close by sending an Expires header or a
Cache-Control: max-age directive set far into the future.

The RFC 2616 (HTTP/1.1) has a note on this practice:

To mark a response as "never expires," an origin server sends
an Expires date approximately one year from the time the
response is sent. HTTP/1.1 servers SHOULD NOT send Expires
dates more than one year in the future.

-- 14.21 Expires, RFC 2616


The directives below will prompt Apache to send both an Expires and
Cache-Control header, instructing caches to treat all PNG images
(image/png) as fresh for 365 days from the time of access. That is, each
time a request is made to the origin server, a different expiry date
will be calculated.

ExpiresActive On
ExpiresByType image/png A31536000

These directives require the mod_expires module.

Hope that helps,
Mike

--
Michael Winter
Prefix subject with [News] before replying by e-mail.

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