Description of the Cache-control parameter in the header

The cache of the Web page is controlled by the "Cache-control" in the HTTP message header, and the common values are private, No-cache, Max-age, must-revalidate, etc., and the default is private. Its function is divided into the following situations according to different ways of re-browsing:

(1) Open a new window

The value is private, No-cache, Must-revalidate, and the server will be re-accessed when a new window is opened.

If you specify a max-age value, the server is not re-accessed in the time within this value, for example:

Cache-control:max-age=5 (indicates that access will not go to the server within 5 seconds of accessing this page)

(2) Enter in the Address bar

A value of private or must-revalidate will only access the server on the first visit and will no longer be accessed at a later time.

The value is No-cache, which is accessed every time.

A value of max-age, the access is not repeated until it expires.

(3) Press Back button

The value is private, must-revalidate, Max-age, and is not re-accessed.

A value of No-cache, which is repeatedly accessed every time

(4) Press the Refresh button

No matter what the value, it will be accessed repeatedly

When the Cache-control value is "No-cache", accessing this page does not leave a page backup in the Temporary Internet Article folder.

Also, the cache is affected by specifying a value of "Expires". For example, specifying the Expires value is a time long past, then when you visit this network repeatedly press ENTER in the Address bar, then each time will be repeated access: Expires:fri, Dec 1999 16:00:00 GMT

For example: Prevent pages from being cached in IE

HTTP response message Header settings:

CacheControl = No-cache

Pragma=no-cache

Expires =-1

Expires is a good thing, if the Web page on the server changes frequently, it is set to 1, indicating immediate expiration. If a webpage is updated daily 1 o'clock in the morning, you can set expires to 1 o'clock in the morning the next day.

When the HTTP1.1 server specifies CacheControl = No-cache, the browser does not cache the page.

Legacy HTTP 1.0 Servers cannot use the Cache-control header.

So for backwards compatibility with HTTP 1.0 servers, IE uses the Pragma:no-cache header to provide special support for HTTP.

If the client communicates with the server over a secure connection (https://) and the server returns the Pragma:no-cache header in the response,

Internet Explorer does not cache this response. Note: Pragma:no-cache prevents caching only when used in a secure connection, and if used in a non-secure page, is processed in the same way as expires:-1, the page is cached but is marked for immediate expiration.

Description of the Cache-control parameter in the header