I've got a resource in my Nginx that is configured like this:
location ~ foo\.js$ { add_header Cache-Control public; expires 1d; }
If I open this with Firebug and look at the headers it shows this:
Cache-Control max-age=86400, public
The site is using HTTPS so I want to make sure I get it right because apparently browsers don't cache it unless it's max-age>0 AND public
. See this
But what happens with my Nginx when I use curl -Ik https://...
is that it says:
... Expires: Sat, 22 Jan 2011 18:23:36 GMT Cache-Control: max-age=86400 Cache-Control: public ...
It repeats the Cache-Control
header! Clearly Firebug doesn't mind. But is it right?
Is there a perhaps a better way to set Expires
and Cache-Control
(with public
) in one just two lines?
If you want to enable Cache-Control for all files, add a add_header line without the enclosing location block, as what the location block does is specify specific filetypes you are targeting with your directives (ico,pdf,flv etc.).
Without the cache control header the browser requests the resource every time it loads a new(?) page.
To use cache-control in HTML, you use the meta tag, e.g. The value in the content field is defined as one of the four values below. HTTP 1.1. Allowed values = PUBLIC | PRIVATE | NO-CACHE | NO-STORE.
Cache-Control: max-age=<seconds> This directive tells the browser or intermediary cache how long the response can be used from the time it was requested. A max-age of 3600 means that the response can be used for the next 60 minutes before it needs to fetch a new response from the origin server.
Yes, it's valid and equivalent to use multiple Cache-Control headers.
From the HTTP 1.1 spec:
Multiple message-header fields with the same field-name MAY be present in a message if and only if the entire field-value for that header field is defined as a comma-separated list [i.e., #(values)]. It MUST be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics of the message, by appending each subsequent field-value to the first, each separated by a comma.
It's easy to verify that this provision applies to the Cache-Control header because of how it's defined:
Cache-Control = "Cache-Control" ":" 1#cache-directive
To understand how to interpret the line above, see the spec's notational conventions. The 1#
means "a comma-separated list of one or more".
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