max-age
    When an intermediate cache is forced, by means of a max-age=0 directive, to revalidate 
its own cache entry, and the client has supplied its own validator in the request, the 
supplied validator might differ from the validator currently stored with the cache entry. 
In this case, the cache MAY use either validator in making its own request without 
affecting semantic transparency. 

    However, the choice of validator might affect performance. The best approach is for the 
intermediate cache to use its own validator when making its request. If the server replies 
with 304 (Not Modified), then the cache can return its now validated copy to the client 
with a 200 (OK) response. If the server replies with a new entity and cache validator, 
however, the intermediate cache can compare the returned validator with the one provided in 
the client's request, using the strong comparison function. If the client's validator is 
equal to the origin server's, then the intermediate cache simply returns 304 (Not 
Modified). Otherwise, it returns the new entity with a 200 (OK) response. 

    If a request includes the no-cache directive, it SHOULD NOT include min-fresh, 
max-stale, or max-age. 

礼貌:http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html # sec14.9.4

不要接受这个答案-我必须读它才能理解它的真正用法:)

信息= 0

这相当于单击Refresh，这意味着给我最新的副本，除非我已经有了最新的副本。

no - cache

这是按住Shift同时点击刷新，这意味着，不管发生什么都要重做。

One thing that (surprisingly) hasn't been mentioned is that a request can explicitly indicate that it will accept stale data, using the max-stale directive. In that case, if the server responded with max-age=0, the cache would merely consider the response stale, and would be free to use it to satisfy the client's request [which asked for potentially-stale data]. By contrast, if the server sends no-cache that really does trump any request by the client (with max-stale) for stale data, as the cache MUST revalidate.

顺便说一下，值得注意的是，一些移动设备，特别是苹果产品，如iPhone/iPad完全忽略了诸如no-cache, no-store, Expires: 0或其他任何你可能试图强迫他们不要重用过期表单页面的头文件。

This has caused us no end of headaches as we try to get the issue of a user's iPad say, being left asleep on a page they have reached through a form process, say step 2 of 3, and then the device totally ignores the store/cache directives, and as far as I can tell, simply takes what is a virtual snapshot of the page from its last state, that is, ignoring what it was told explicitly, and, not only that, taking a page that should not be stored, and storing it without actually checking it again, which leads to all kinds of strange Session issues, among other things.

我只是为了防止有人不知道为什么他们会在iphone和ipad上出现会话错误，这似乎是迄今为止最严重的问题。

关于这个问题，我已经做了相当广泛的调试器测试，这是我的结论，设备完全忽略了这些指令。

即使在日常使用中，我发现一些手机也完全无法检查新版本，例如，过期:0，然后检查最近修改的日期，以确定是否应该获得一个新的版本。

它根本不会发生，所以我被迫做的是向我需要强制更新的css/js文件添加查询字符串，这欺骗了愚蠢的移动设备，认为这是一个它没有的文件，比如:my.css?V =1，然后V =2的css/js更新。这在很大程度上是有效的。

User browsers also, by the way, if left to their defaults, as of 2016, as I continuously discover (we do a LOT of changes and updates to our site) also fail to check for last modified dates on such files, but the query string method fixes that issue. This is something I've noticed with clients and office people who tend to use basic normal user defaults on their browsers, and have no awareness of caching issues with css/js etc, almost invariably fail to get the new css/js on change, which means the defaults for their browsers, mostly MSIE / Firefox, are not doing what they are told to do, they ignore changes and ignore last modified dates and do not validate, even with Expires: 0 set explicitly.

这是一个很好的帖子，包含了很多很好的技术信息，但同样重要的是要注意到这些东西在移动设备上的支持有多差。每隔几个月，我就必须增加更多的保护层，防止他们无法遵循他们收到的头命令，或者正确地解释这些命令。

我也有同样的问题，在我的搜索中找到了一些信息(你的问题是结果之一)。这是我的决定……

Cache-Control头有两个面。一边是它可以发送的web服务器(aka。“原始服务器”)。另一边是浏览器可以发送数据的地方。“用户代理”)。

当由源服务器发送时

我相信max-age=0只是告诉缓存(和用户代理)响应从一开始就过时了，所以他们应该重新验证响应。使用If-Not-Modified头)在使用缓存副本之前，而no-cache告诉他们在使用缓存副本之前必须重新验证。从14.9.1什么是可缓存的

no - cache .．.缓存绝对不能使用响应 满足后续的请求 没有成功的重新验证 源服务器。这允许 源服务器防止缓存甚至 通过已配置为 向客户端返回过时的响应 请求。

换句话说，缓存有时可能会选择使用过时的响应(尽管我认为它们必须添加一个警告标头)，但无缓存表示无论如何都不允许使用过时的响应。在页面中生成棒球统计数据时，您可能希望使用SHOULD-revalidate行为，但在生成对电子商务购买的响应时，可能希望使用MUST-revalidate行为。

虽然您在评论中说无缓存不应该阻止存储是正确的，但在使用无缓存时，这实际上可能是另一个区别。我看到一个页面，缓存控制指令解密，上面写着(我不能保证它的正确性):

实际上，IE和Firefox已经做到了 开始处理无缓存 指令就好像它在指令 浏览器甚至不缓存页面。 我们开始观察这种行为 大约一年前。我们怀疑 这一变化是由 广泛的(不正确的)使用 指令防止缓存。 .．. 请注意，最近，“cache-control: “无缓存”也开始发挥作用 比如“禁止存放”的指令。

顺便说一句，在我看来，Cache-Control: max-age=0, must-revalidate基本上应该与Cache-Control: no-cache意思相同。因此，也许这是一种获得无缓存的MUST-revalidate行为的方法，同时避免将无缓存迁移到与无存储(即无存储)相同的事情。没有缓存)?

当由用户代理发送时

我相信shahkalpesh的答案适用于用户代理端。你也可以看看13.2.6消除多个响应的歧义。

如果一个用户代理用Cache-Control发送一个请求:max-age=0 (aka。“端到端重新验证”)，然后沿途的每个缓存将重新验证其缓存条目(例如。使用If-Not-Modified报头)一直到源服务器。如果回复是304 (Not Modified)，则可以使用缓存的实体。

另一方面，发送请求与Cache-Control: no-cache (aka。“端到端重新加载”)不会重新验证，服务器在响应时绝对不能使用缓存副本。

这在MDN文档中直接回答了缓存控制:

大多数HTTP/1.0缓存不支持无缓存指令，所以 历史上max-age=0被用作一种变通方法。但只有 Max-age =0可能会导致在缓存时重用一个陈旧的响应 与源服务器断开连接。必须重新验证才能解决这个问题。 这就是为什么下面的例子等同于无缓存。 Cache-Control: max-age=0，必须重新验证 但是现在，您可以简单地使用无缓存代替。

在MDN文档中也有缓存验证:

It is often stated that the combination of max-age=0 and must-revalidate has the same meaning as no-cache. Cache-Control: max-age=0, must-revalidate max-age=0 means that the response is immediately stale, and must-revalidate means that it must not be reused without revalidation once it is stale — so in combination, the semantics seem to be the same as no-cache. However, that usage of max-age=0 is a remnant of the fact that many implementations prior to HTTP/1.1 were unable to handle the no-cache directive — and so to deal with that limitation, max-age=0 was used as a workaround. But now that HTTP/1.1-conformant servers are widely deployed, there's no reason to ever use that max-age=0-and-must-revalidate combination — you should instead just use no-cache.