is meta http-equiv value cache control is not supported?

Question

i have this code here on a page:

Answer 1

Only some headers are supported through the http-equiv attribute, and support is different in different browsers. For example, Mozilla only document support for:

• content-language
• Content-Security-Policy
• content-type
• default-style
• refresh
• set-cookie

The intention was for servers to parse this header (meta http-equiv - is it sent as part of an HTTP header, or does the client parse the body for meta tags?), but this was never widely implemented. It is implemented by Apache httpd's mod_proxy:

The other effect of enabling ProxyHTMLMeta is to parse all <meta http-equiv=...> declarations and convert them to real HTTP headers, in keeping with the original purpose of this form of the HTML <meta> element.

Using <meta> tags to turn off caching in all browsers? suggests a format that may work in more browsers but, in general, this is not a supported technique.

Answer 2

The <meta http-equiv> tags are only used when the HTML file in question is been opened from a non-HTTP resource such as local disk file system (via file:// URI) and not when the HTML file in question is been opened from a real HTTP resource (via http:// URI). Instead, the real HTTP response headers as set via HttpServletResponse#setHeader() are been used.

So, your concrete problem is caused because those <meta http-equiv> tags are ignored.

See also:

• How to control web page caching, across all browsers?
• Avoid back button on JSF web application