Http 304 Error Wiki
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be returned if allowed by the client (e.g. your Web browser or our CheckUpDown robot). The client specifies this in the HTTP data stream sent to the Web server e.g. via If_Modified_Since headers in http error code the request. Systems that cache or index Web resources (such as search engines) often use http code 403 the 304 response to determine if the information they previously gathered for a particular URL is now out-of-date. Fixing 304 errors -
Http Code 302
general You should never see this error in your Web browser. It should simply present the Web page from its cache - because it believes the page has not changed since it was last cached. If your
Http Response Example
client is not a Web browser, then it should equally be able to present the page from a cache. If unable to do so, it is not using the If_Modified_Since or related headers correctly. Fixing 304 errors - CheckUpDown You should never see this error at all for the CheckUpDown service. It indicates defective programming by us or the developers of the Web server software. Either we or they are not respecting HTTP protocols http status codes cheat sheet completely. The 304 status code should only be returned if we allow it in the HTTP data stream we send to the Web server. Because we keep no records of the actual content of your URL Web page, we specifically disallow the 304 response in the HTTP data stream we send. So if the Web server implements the HTTP protocol properly, it should never send an 304 status code back to us. This response is not what we expect, so we actively report it as an error even though it does not necessarily mean that the Web site is down. Please contact us directly (email preferred) whenever you encounter 304 errors. Only we can resolve them for you. Unfortunately this may take some time, because we have to analyse the underlying HTTP data streams and may have to liaise with your ISP and the vendor of the Web server software to agree the exact source of the error. 304 errors in the HTTP cycle Any client (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle when it communicates with the Web server: Obtain an IP address from the IP name of the site (the site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs). Open
false. In other words, there is no need for the server to transfer a
Http 504
representation of the target resource because the request indicates that http 422 the client, which made the request conditional, already has a valid representation; the server is therefore http 502 redirecting the client to make use of that stored representation as if it were the payload of a 200 OK response. The server generating a http://www.checkupdown.com/status/E304.html 304 response MUST generate any of the following header fields that would have been sent in a 200 OK response to the same request: Cache-Control, Content-Location, Date, ETag, Expires, and Vary. Since the goal of a 304 response is to minimize information transfer when the recipient already has one or more cached https://httpstatuses.com/304 representations, a sender SHOULD NOT generate representation metadata other than the above listed fields unless said metadata exists for the purpose of guiding cache updates (e.g., Last-Modified might be useful if the response does not have an ETag field). Requirements on a cache that receives a 304 response are defined in Section 4.3.4 of RFC7234. If the conditional request originated with an outbound client, such as a user agent with its own cache sending a conditional GET to a shared proxy, then the proxy SHOULD forward the 304 response to that client. A 304 response cannot contain a message-body; it is always terminated by the first empty line after the header fields. Source: RFC7232 Section 4.1 304 Code References Rails HTTP Status Symbol :not_modified Go HTTP Status Constant http.StatusNotModified Symfony HTTP Status Constant Response::HTTP_NOT_MODIFIED Python2 HTTP Status Constant httplib.NOT_MODIFIED Python3+ HTTP Status Constant http.client.NOT_MODIFIED Python3.5+ HTTP Status Constant http.HTTPStatus.NOT_MODIFIED← Return to httpstatuses.com
consisting only of the Status-Line and optional headers, and is terminated by an empty line. There are no required headers for this class of status code. Since HTTP/1.0 did not define any 1xx status http://www.restapitutorial.com/httpstatuscodes.html codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client except under experimental conditions. A client MUST be prepared to accept one or more 1xx status responses prior to a regular response, even if the client does not expect a 100 (Continue) status message. Unexpected 1xx status responses MAY be ignored by a user agent. Proxies MUST forward 1xx responses, unless the connection between the proxy and its client has been closed, http code or unless the proxy itself requested the generation of the 1xx response. (For example, if a proxy adds a "Expect: 100-continue" field when it forwards a request, then it need not forward the corresponding 100 (Continue) response(s).) Wikipedia Request received, continuing process. This class of status code indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line. Since HTTP/1.0 did not define any 1xx status http 304 error codes, servers must not send a 1xx response to an HTTP/1.0 client except under experimental conditions. 100 Continue The client SHOULD continue with its request. This interim response is used to inform the client that the initial part of the request has been received and has not yet been rejected by the server. The client SHOULD continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The server MUST send a final response after the request has been completed. See section 8.2.3 for detailed discussion of the use and handling of this status code. Wikipedia This means that the server has received the request headers, and that the client should proceed to send the request body (in the case of a request for which a body needs to be sent; for example, a POST request). If the request body is large, sending it to a server when a request has already been rejected based upon inappropriate headers is inefficient. To have a server check if the request could be accepted based on the request's headers alone, a client must send Expect: 100-continue as a header in its initial request and check if a 100 Continue status code is received in response before continuing (or receive 417 Expectation Failed and not conti