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The Cache-Control: no-cache HTTP/1.1 header field is also intended for use in requests made by the client. It is a means for the browser to tell the server and any intermediate caches that it wants a fresh version of the resource. The Pragma: no-cache header field, defined in the HTTP/1.0 spec, has the same purpose. It, however, is only defined ...
Unlike the other status codes above, these were not sent as the response status in the HTTP protocol, but as part of the "Warning" HTTP header. [ 56 ] [ 57 ] Since this "Warning" header is often neither sent by servers nor acknowledged by clients, this header and its codes were obsoleted by the HTTP Working Group in 2022 with RFC 9111 .
Each response header field has a defined meaning which can be further refined by the semantics of the request method or response status code. HTTP/1.1 example of request / response transaction Below is a sample HTTP transaction between an HTTP/1.1 client and an HTTP/1.1 server running on www.example.com , port 80.
The HTTP Location header field is returned in responses from an HTTP server under two circumstances: To ask a web browser to load a different web page (URL redirection). In this circumstance, the Location header should be sent with an HTTP status code of 3xx. It is passed as part of the response by a web server when the requested URI has:
For a subsequent request that would've included the If-None-Match header, do not send this header with perhaps a random 20% probability. With this probability, if the response returns an altered content but the same ETag as what was previously cached, mark the website as buggy and disable ETag caching for it.
Headers; An empty line; Optional HTTP message body data; The request/status line and headers must all end with <CR><LF> (that is, a carriage return followed by a line feed). The empty line must consist of only <CR><LF> and no other whitespace. The "optional HTTP message body data" is what this article defines.
The meta element has two uses: either to emulate the use of an HTTP response header field, or to embed additional metadata within the HTML document. With HTML up to and including HTML 4.01 and XHTML, there were four valid attributes: content, http-equiv, name and scheme. Under HTML 5, charset has been added and scheme has been removed.
The HTTP response status code 302 Found is a common way of performing URL redirection. The HTTP/1.0 specification (RFC 1945) initially defined this code, and gave it the description phrase "Moved Temporarily" rather than "Found". An HTTP response with this status code will additionally provide a URL in the header field Location.