blocks|key|210833|text|Cache-Control:+private|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|210834|unstyled|210835|指示所有或部分响应消息是针对单个用户的，并且不能由共享缓存(如代理服务器)进行缓存。|blockquote|210836|210837|210838|来自RFC2616+section+14.9.1|offset|length|210839|entityMap|0|LINK|mutability|MUTABLE|url|http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html^0|0|0|0|0|0|2|M|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|X|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|Y|8|@]|9|@]|A|$]]|$1|I|3|-4|5|E|7|Z|8|@]|9|@]|A|$]]|$1|J|3|-4|5|E|7|10|8|@]|9|@]|A|$]]|$1|K|3|L|5|E|7|11|8|@]|9|@$M|12|N|13|1|14]]|A|$]]|$1|O|3|-4|5|E|7|15|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

<pre><code>Cache-Control: private
</code></pre>

<blockquote>
 Indicates that all or part of the response message is intended for a single user and MUST NOT be cached by a shared cache, such as a proxy server.
</blockquote>

From <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html" rel="noreferrer">RFC2616 section 14.9.1</a>

blocks|key|3064022|text|RFC2616，section+14.9.1|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3064023|3064024|表示所有或部分响应消息是针对单个用户的，不能由共享缓存缓存...私有(非共享)缓存可以缓存响应。|blockquote|3064025|3064026|3064027|3064028|浏览器可以使用此信息。当然，当前的“用户”可能意味着很多东西:操作系统用户、浏览器用户(例如Chrome的配置文件)等等。|3064029|对我来说，+Cache-Control:+private的一个更具体的例子是代理服务器(通常有很多用户)不会缓存它。它是为最终用户设计的，而不是其他人。|style|BOLD|CODE|3064030|3064031|仅供参考，RFC明确表示这不提供安全性。它是关于显示正确的内容，而不是保护内容。|3064032|3064033|专用一词的这种用法仅控制可以缓存响应的位置，不能确保消息内容的私密性。|3064034|3064035|entityMap|0|LINK|mutability|MUTABLE|url|http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9.1^0|8|E|0|0|0|0|0|0|0|0|6|V|6|M|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@$A|17|B|18|1|19]]|C|$]]|$1|D|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|1B|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|1D|8|@]|9|@]|C|$]]|$1|J|3|-4|5|6|7|1E|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|1F|8|@]|9|@]|C|$]]|$1|M|3|N|5|6|7|1G|8|@$A|1H|B|1I|O|P]|$A|1J|B|1K|O|Q]]|9|@]|C|$]]|$1|R|3|-4|5|6|7|1L|8|@]|9|@]|C|$]]|$1|S|3|T|5|6|7|1M|8|@]|9|@]|C|$]]|$1|U|3|-4|5|6|7|1N|8|@]|9|@]|C|$]]|$1|V|3|W|5|G|7|1O|8|@]|9|@]|C|$]]|$1|X|3|-4|5|6|7|1P|8|@]|9|@]|C|$]]|$1|Y|3|-4|5|6|7|1Q|8|@]|9|@]|C|$]]]|Z|$10|$5|11|12|13|C|$14|15]]]]

RFC 2616, <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9.1">section 14.9.1</a>:

<blockquote>
 Indicates that all or part of the response message is intended for a single user and MUST NOT be cached by a shared cache...A private (non-shared) cache MAY cache the response.
</blockquote>

<hr>

Browsers could use this information. Of course, the current "user" may mean many things: OS user, a browser user (e.g. Chrome's profiles), etc. It's not specified.

For me, a more concrete example of <code>Cache-Control: private</code> is that proxy servers (which typically have many users) won't cache it. It is meant for the end user, and no one else.

<hr>

FYI, the RFC makes clear that this does not provide security. It is about showing the correct content, not securing content.

<blockquote>
 This usage of the word private only controls where the response may be cached, and cannot ensure the privacy of the message content.
</blockquote>

blocks|key|208153|text|Expires+entity-header字段提供响应被视为过期的日期/时间:+stale.The缓存控制:MaxAge值(以秒为单位)大于响应被视为陈旧的时间值。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|208154|虽然上面的头部字段提供了一种机制，让客户端决定是否向服务器发送请求。在某些情况下，客户端向服务器发送请求，并且响应的年龄值大于最大值，这是否意味着服务器需要将资源发送给客户端？也许资源永远不会改变。|208155|为了解决这个问题，HTTP1.1给出了最后修改的报头。服务器将响应的最后修改日期提供给客户端。当客户端需要该资源时，它会向服务器发送If-Modified-+send报头字段。如果此日期早于资源的修改日期，则服务器会将资源发送给客户端，并提供200+code.Otherwise，它将向客户端返回304代码，这意味着客户端可以使用它缓存的资源。|208156|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

The Expires entity-header field gives the date/time after which the response is considered stale.The Cache-control:maxage field gives the age value (in seconds) bigger than which response is consider stale. 

Althought above header field give a mechanism to client to decide whether to send request to the server. In some condition, the client send a request to sever and the age value of response is bigger then the maxage value ,dose it means server needs to send the resource to client? Maybe the resource never changed.

In order to resolve this problem, HTTP1.1 gives last-modifided head. The server gives the last modified date of the response to client. When the client need this resource, it will send If-Modified-Since head field to server. If this date is before the modified date of the resouce, the server will sends the resource to client and gives 200 code.Otherwise,it will returns 304 code to client and this means client can use the resource it cached.

When I visit <a href="http://chesseng.herokuapp.com" rel="noreferrer">chesseng.herokuapp.com</a> I get a response header that looks like

<pre><code>Cache-Control:private
Connection:keep-alive
Content-Encoding:gzip
Content-Type:text/css
Date:Tue, 16 Oct 2012 06:37:53 GMT
Last-Modified:Tue, 16 Oct 2012 03:13:38 GMT
Status:200 OK
transfer-encoding:chunked
Vary:Accept-Encoding
X-Rack-Cache:miss
</code></pre>

and then I refresh the page and get

<pre><code>Cache-Control:private
Connection:keep-alive
Date:Tue, 16 Oct 2012 06:20:49 GMT
Status:304 Not Modified
X-Rack-Cache:miss
</code></pre>

so it seems like caching is working. If that works for caching then what is the point of Expires and Cache-Control:max-age. To add to confusion, when I test the page at <a href="https://developers.google.com/speed/pagespeed/insights" rel="noreferrer">https://developers.google.com/speed/pagespeed/insights/</a> it tells me to "Leverage browser caching".

What is Cache-Control: private?

当我访问时，我得到一个响应头，如下所示Cache-Control:privateConnection:keep-aliveContent-Encoding:gzipContent-Type:text/cssDate:Tue, 16 Oct 2012 06:37:53 GMTLast-Modified:Tue, 16 O...

问什么是Cache-Control: private？
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