HTTP Status Codes - Part 3 of Chapter 3 from HTTP: The Definitive Guide

Status code	Reason phrase	Meaning
300	Multiple Choices	Returned when a client has requested a URL that actually refers to multiple resources, such as a server hosting an English and French version of an HTML document. This code is returned along with a list of options; the user can then select which one he wants. See Chapter 17 for more on clients negotiating when there are multiple versions. The server can include the preferred URL in the Location header.
301	Moved Permanently	Used when the requested URL has been moved. The response should contain in the Location header the URL where the resource now resides.
302	Found	Like the 301 status code; however, the client should use the URL given in the Location header to locate the resource temporarily. Future requests should use the old URL.
303	See Other	Used to tell the client that the resource should be fetched using a different URL. This new URL is in the Location header of the response message. Its main purpose is to allow responses to POST requests to direct a client to a resource.
304	Not Modified	Clients can make their requests conditional by the request headers they include. See Table 3-15 for more on conditional headers. If a client makes a conditional request, such as a GET if the resource has not been changed recently, this code is used to indicate that the resource has not changed. Responses with this status code should not contain an entity body.
305	Use Proxy	Used to indicate that the resource must be accessed through a proxy; the location of the proxy is given in the Location header. It's important that clients interpret this response relative to a specific resource and do not assume that this proxy should be used for all requests or even all requests to the server holding the requested resource. This could lead to broken behavior if the proxy mistakenly interfered with a request, and it poses a security hole.
306	(Unused)	Not currently used.
307	Temporary Redirect	Like the 301 status code; however, the client should use the URL given in the Location header to locate the resource temporarily. Future requests should use the old URL.

Status code

Reason phrase

Meaning

300

Multiple Choices

Returned when a client has requested a URL that actually refers to multiple resources, such as a server hosting an English and French version of an HTML document. This code is returned along with a list of options; the user can then select which one he wants. See Chapter 17 for more on clients negotiating when there are multiple versions. The server can include the preferred URL in the Location header.

301

Moved Permanently

Used when the requested URL has been moved. The response should contain in the Location header the URL where the resource now resides.

302

Found

Like the 301 status code; however, the client should use the URL given in the Location header to locate the resource temporarily. Future requests should use the old URL.

303

See Other

Used to tell the client that the resource should be fetched using a different URL. This new URL is in the Location header of the response message. Its main purpose is to allow responses to POST requests to direct a client to a resource.

304

Not Modified

Clients can make their requests conditional by the request headers they include. See Table 3-15 for more on conditional headers. If a client makes a conditional request, such as a GET if the resource has not been changed recently, this code is used to indicate that the resource has not changed. Responses with this status code should not contain an entity body.

305

Use Proxy

Used to indicate that the resource must be accessed through a proxy; the location of the proxy is given in the Location header. It's important that clients interpret this response relative to a specific resource and do not assume that this proxy should be used for all requests or even all requests to the server holding the requested resource. This could lead to broken behavior if the proxy mistakenly interfered with a request, and it poses a security hole.

306

(Unused)

Not currently used.

307

Temporary Redirect

Like the 301 status code; however, the client should use the URL given in the Location header to locate the resource temporarily. Future requests should use the old URL.