Table 275 lists in numerical order the status codes defined by the HTTP/1.1 standard, along with the “standard” reason phrase and a brief description of each:

Table 275: HTTP Status Codes

Status
Code

Reason
Phrase

Description

100

Continue

Client should continue sending
its request. This is a special status code; see below for details.

101

Switching
Protocols

The client
has used the Upgrade header to request the use of an alternative
protocol and the server has agreed.

200

OK

Generic successful request message
response. This is the code sent most often when a request is filled
normally.

201

Created

The request
was successful and resulted in a resource being created. This would
be a typical response to a PUT method.

202

Accepted

The request was accepted by the
server but has not yet been processed. This is an intentionally “non-commital”
response that does not tell the client whether or not the request will
be carried out; the client determines the eventual disposition of the
request in some unspecified way. It is used only in special circumstances.

203

Non-Authoritative
Information

The request
was successful, but some of the information returned by the server came
not from the original server associated with the resource but from a
third party.

204

No Content

The request was successful, but
the server has determined that it does not need to return to the client
an entity body.

205

Reset
Content

The request
was successful; the server is telling the client that it should reset
the document from which the request was generated so that a duplicate
request is not sent. This code is intended for use with forms.

206

Partial Content

The server has successfully fulfilled
a partial GET request.
See the topic
on methods
for more details on this, as
well as
the description
of the Range header
.

300

Multiple
Choices

The resource
is represented in more than one way on the server. The server is returning
information describing these representations, so the client can pick
the most appropriate one, a process called
agent-driven
negotiation
.

301

Moved Permanently

The resource requested has been
moved to a new URL permanently. Any future requests for this resource
should use the new URL.

This is the proper method of handling situations where a file on a server
is renamed or moved to a new directory. Most people don’t bother setting
this up, which is why URLs “break” so often, resulting in
404 errors as discussed below.

302

Found

The resource
requested is temporarily using a different URL. The client should continue
to use the original URL. See code 307.

303

See Other

The response for the request
can be found at a different URL, which the server specifies. The client
must do a fresh GET on that URL to see the results of the prior
request.

304

Not
Modified

The client
sent a conditional GET request, but the resource has not been
modified since the specified date/time, so the server has not sent it.

305

Use Proxy

To access the requested resource,
the client must use a proxy, whose URL is given by the server in its
response.

306

(unused)

Defined in
an earlier (draft?) version of HTTP and no longer used.

307

Temporary Redirect

The resource is temporarily located
at a different URL than the one the client specified.

Note that 302 and 307 are basically the same status code. 307 was created
to clear up some confusion related to 302 that occurred in earlier versions
of HTTP (which I’d rather not get into!)

400

Bad
Request

Server says,
“huh?”
J
Generic response when the request cannot be understood or carried out
due to a problem on the client’s end.

401

Unauthorized

The client is not authorized
to access the resource. Often returned if an attempt is made to access
a resource protected by a password or some other means without the appropriate
credentials.

402

Payment
Required

This is reserved
for future use. Its mere presence in the HTTP standard has caused a
lot of people to scratch their chins and go “hmm…”
J

403

Forbidden

The request has been disallowed
by the server. This is a generic “no way” response that is
not related to authorization. For example, if the maintainer of Web
site blocks access to it from a particular client, any requests from
that client will result in a 403 reply.

404

Not
Found

The most common
HTTP error message, returned when the server cannot locate the requested
resource. Usually occurs due to either the server having moved/removed
the resource, or the client giving an invalid URL (misspellings being
the most common cause.)

405

Method Not Allowed

The requested method is not allowed
for the specified resource. The response includes an Allow header
that indicates what methods the server will permit.

406

Not
Acceptable

The client
sent a request that specifies limitations that the server cannot meet
for the specified resource. This error may occur if an overly-restrictive
list of conditions is placed into a request such that the server cannot
return any part of the resource.

407

Proxy Authentication
Required

Similar to 401, but the client
must first authenticate itself with the
proxy.

408

Request
Timeout

The server
was expecting the client to send a request within a particular time
frame and the client didn’t send it.

409

Conflict

The request could not be filled
because of a conflict of some sort related to the resource. This most
often occurs in response to a PUT method, such as if one user
tries to PUT a resource that another user has open for editing,
for example.

410

Gone

The resource
is no longer available at the server, which does not know its new URL.
This is a more specific version of the 404 code that is used only if
the server knows that the resource was intentionally removed. It is
seen rarely (if ever) compared to 404.

411

Length Required

The request requires a Content-Length
header field
and one was not included.

412

Precondition
Failed

Indicates that
the client specified a precondition in its request, such as the use
of an If-Match header, which evaluated to a false value. This
indicates that the condition was not satisfied so the request is not
being filled. This is used by clients in special cases to ensure that
they do not accidentally receive the wrong resource.

413

Request Entity
Too Large

The server has refused to fulfill
the request because the entity that the client is requesting is too
large.

414

Request-URI
Too Long

The server
has refused to fulfill the request because the URL specified is longer
than the server can process. This rarely occurs with properly-formed
URLs but may be seen if clients try to send gibberish to the server.

415

Unsupported
Media Type

The request cannot be processed
because it contains an entity using a media type the server does not
support.

416

Requested
Range Not Satisfiable

The client
included a Range header specifying a range of values that is
not valid for the resource. An example might be requesting bytes 3,000
through 4,000 of a 2,400-byte file.

417

Expectation
Failed

The request included an Expect
header that could not be satisfied by the server.

500

Internal
Server Error

Generic error
message indicating that the request could not be fulfilled due to a
server problem.

501

Not Implemented

The server does not know how
to carry out the request, so it cannot satisfy it.

502

Bad
Gateway

The server,
while acting as a gateway or proxy, received an invalid response from
another server it tried to access on the client’s behalf.

503

Service Unavailable

The server is temporarily unable
to fulfill the request for internal reasons. This is often returned
when a server is overloaded or down for maintenance.

504

Gateway
Timeout

The server,
while acting as a gateway or proxy, timed out while waiting for a response
from another server it tried to access on the client’s behalf.

505

HTTP Version
Not Supported

The request used a version of
HTTP that the server does not understand.