meta http-equiv - is it sent as part of an HTTP he

问题:

Wikipedia seems to imply that <meta http-equiv> in a web page causes the server to update the response header, but that doesn't sound right to me since the server would have to parse the document before it's sent. That would be fugly.

But, I'm having trouble finding much on what does happen when when <meta http-equiv> is used. It seems likely to me that the client parses the page and clobbers anything that was sent in the HTTP header if a <meta http-equiv> tag is found conflicts with the header.

Does anybody know what the actual process is and/or have any ideas about where I might find more information about this topic?

Thanks!
Greg

回答1:

Servers were supposed to parse HTML, extract <meta> and send it in real HTTP headers. As you can guess, this isn't implemented in any major web server.

So currently clients read <meta http-equiv>. However, it's not any close to being an "equivalent" of HTTP headers. It only supports a short whitelist of specific values, most of which are for compatibility with legacy content.