status codes

Question 1

What do HTTP response status codes indicate?

Answer 1

How a specific HTTP request has completed.

Question 2

What are the five HTTP status code classes?

Answer 2

1xx: Informational.
2xx: Successful.
3xx: Redirection.
4xx: Client Error.
5xx: Server Error.

Question 3

100 status code?

Answer 3

Continue. Everything is OK so far and client should continue with request or ignore if it is already finished.

Question 4

101 status code?

Answer 4

Switching Protocol. Response to an Upgrade request header by the client, and indicates the protocol the server is switching to.

Question 5

102 status code?

Answer 5

Processing. Indicates that the server has received and is processing the request, but no response is available yet.

Question 6

103 status code?

Answer 6

Early Hints. Primarily intended to be used with the Link header to allow the user agent to start preloading resources while the server is still preparing a response.

Question 7

200 status code?

Answer 7

OK. The request has succeeded. The meaning of a success varies depending on the HTTP method:
GET: The resource has been fetched and is transmitted in the message body.
HEAD: The entity headers are in the message body.
PUT or POST: The resource describing the result of the action is transmitted in the message body.
TRACE: The message body contains the request message as received by the server.

Question 8

201 status code?

Answer 8

Created. Request has succeeded and a new resource has been created as a result of it. This is typically the response sent after a POST request, or after some PUT requests.

Question 9

202 status code?

Answer 9

Accepted. The request has been received but not yet acted upon. It is non-committal, meaning that there is no way in HTTP to later send an asynchronous response indicating the outcome of processing the request. It is intended for cases where another process or server handles the request, or for batch processing.

Question 10

203 status code?

Answer 10

Non-Authoritative Information. Returned meta-information set is not exact set as available from the origin server, but collected from a local or a third party copy. Except this condition, 200 OK response should be preferred instead of this response.

Question 11

204 status code?

Answer 11

No Content. There is no content to send for this request, but the headers may be useful. The user-agent may update its cached headers for this resource with the new ones.

Question 12

205 status code?

Answer 12

Reset Content. Sent after accomplishing request to tell user agent reset document view which sent this request.

Question 13

206 status code?

Answer 13

Partial Content. Used because of range header sent by the client to separate download into multiple streams.

Question 14

300 status code?

Answer 14

Multiple Choice. Request has more than one possible response. The user-agent or user should choose one of them. There is no standardized way of choosing one of the responses.

Question 15

301 status code?

Answer 15

Moved Permanently. Means that the URI of the requested resource has been changed permanently. Probably, the new URI would be given in the response.

Question 16

302 status code?

Answer 16

Found. Means that the URI of requested resource has been changed temporarily. New changes in the URI might be made in the future. Therefore, this same URI should be used by the client in future requests.

Question 17

303 status code?

Answer 17

See Other. The server sent this response to direct the client to get the requested resource at another URI with a GET request.

Question 18

304 status code?

Answer 18

Not Modified. This is used for caching purposes. It tells the client that the response has not been modified, so the client can continue to use the same cached version of the response.

Question 19

307 status code?

Answer 19

Temporary Redirect. The server sends this response to direct the client to get the requested resource at another URI with same method that was used in the prior request. This has the same semantics as the 302 Found HTTP response code, with the exception that the user agent must not change the HTTP method used: If a POST was used in the first request, a POST must be used in the second request.

Question 20

308 status code?

Answer 20

Permanent Redirect. This means that the resource is now permanently located at another URI, specified by the Location: HTTP Response header. This has the same semantics as the 301 Moved Permanently HTTP response code, with the exception that the user agent must not change the HTTP method used: If a POST was used in the first request, a POST must be used in the second request.

Question 21

400 status code?

Answer 21

Bad Request. Means that server could not understand the request due to invalid syntax.

Question 22

401 status code?

Answer 22

Unauthorized. Although the HTTP standard specifies “unauthorized”, semantically this response means “unauthenticated”. That is, the client must authenticate itself to get the requested response.

Question 23

403 status code?

Answer 23

Forbidden. The client does not have access rights to the content, i.e. they are unauthorized, so server is rejecting to give proper response. Unlike 401, the client’s identity is known to the server.

Question 24

404 status code?

Answer 24

Not Found. The server can not find requested resource. In the browser, this means the URL is not recognized. In an API, this can also mean that the endpoint is valid but the resource itself does not exist. Servers may also send this response instead of 403 to hide the existence of a resource from an unauthorized client. This response code is probably the most famous one due to its frequent occurence on the web.

Question 25

405 status code?

Answer 25

Method Not Allowed. The request method is known by the server but has been disabled and cannot be used. For example, an API may forbid DELETE-ing a resource. The two mandatory methods, GET and HEAD, must never be disabled and should not return this error code.

Question 26

406 status code?

Answer 26

Not Acceptable. This response is sent when the web server, after performing server-driven content negotiation, doesn’t find any content following the criteria given by the user agent.

Question 27

407 status code?

Answer 27

Proxy Authentication Required. This is similar to 401 but authentication is needed to be done by a proxy.

Question 28

408 status code?

Answer 28

Request Timeout. This response is sent on an idle connection by some servers, even without any previous request by the client. It means that the server would like to shut down this unused connection. This response is used much more since some browsers, like Chrome, Firefox 27+, or IE9, use HTTP pre-connection mechanisms to speed up surfing. Also note that some servers merely shut down the connection without sending this message.

Question 29

409 status code?

Answer 29

Conflict. This response is sent when a request conflicts with the current state of the server.

Question 30

410 status code?

Answer 30

Gone. This response would be sent when the requested content has been permanently deleted from server, with no forwarding address. Clients are expected to remove their caches and links to the resource. The HTTP specification intends this status code to be used for “limited-time, promotional services”. APIs should not feel compelled to indicate resources that have been deleted with this status code.

Question 31

411 status code?

Answer 31

Length Required. Server rejected the request because the Content-Length header field is not defined and the server requires it.

Question 32

412 status code?

Answer 32

Precondition Failed. The client has indicated preconditions in its headers which the server does not meet.

Question 33

413 status code?

Answer 33

Payload Too Large. Request entity is larger than limits defined by server; the server might close the connection or return an Retry-After header field.

Question 34

414 status code?

Answer 34

URI Too Long. The URI requested by the client is longer than the server is willing to interpret.

Question 35

415 status code?

Answer 35

Unsupported Media Type. The media format of the requested data is not supported by the server, so the server is rejecting the request.

Question 36

416 status code?

Answer 36

Requested Range Not Satisfiable. The range specified by the Range header field in the request can’t be fulfilled; it’s possible that the range is outside the size of the target URI’s data.

Question 37

417 status code?

Answer 37

Expectation Failed. This response code means the expectation indicated by the Expect request header field can’t be met by the server.

Question 38

422 status code?

Answer 38

Unprocessable Entity. The request was well-formed but was unable to be followed due to semantic errors.

Question 39

425 status code?

Answer 39

Too Early. Indicates that the server is unwilling to risk processing a request that might be replayed.

Question 40

426 status code?

Answer 40

Upgrade Required. The server refuses to perform the request using the current protocol but might be willing to do so after the client upgrades to a different protocol. The server sends an Upgrade header in a 426 response to indicate the required protocol(s).

Question 41

428 status code?

Answer 41

Precondition Required. The origin server requires the request to be conditional. Intended to prevent the ‘lost update’ problem, where a client GETs a resource’s state, modifies it, and PUTs it back to the server, when meanwhile a third party has modified the state on the server, leading to a conflict.

Question 42

429 status code?

Answer 42

Too Many Requests. The user has sent too many requests in a given amount of time (“rate limiting”).

Question 43

431 status code?

Answer 43

Request Header Fields Too Large. The server is unwilling to process the request because its header fields are too large. The request MAY be resubmitted after reducing the size of the request header fields.

Question 44

451 status code?

Answer 44

Unavailable For Legal Reasons. The user requests an illegal resource, such as a web page censored by a government.

Question 45

500 status code?

Answer 45

Internal Server Error. The server has encountered a situation it doesn’t know how to handle.

Question 46

501 status code?

Answer 46

Not Implemented. The request method is not supported by the server and cannot be handled. The only methods that servers are required to support (and therefore that must not return this code) are GET and HEAD.

Question 47

502 status code?

Answer 47

Bad Gateway. This error response means that the server, while working as a gateway to get a response needed to handle the request, got an invalid response.

Question 48

503 status code?

Answer 48

Service Unavailable. The server is not ready to handle the request. Common causes are a server that is down for maintenance or that is overloaded. Note that together with this response, a user-friendly page explaining the problem should be sent. This responses should be used for temporary conditions and the Retry-After: HTTP header should, if possible, contain the estimated time before the recovery of the service. The webmaster must also take care about the caching-related headers that are sent along with this response, as these temporary condition responses should usually not be cached.

Question 49

504 status code?

Answer 49

Gateway Timeout. This error response is given when the server is acting as a gateway and cannot get a response in time.

Question 50

505 status code?

Answer 50

HTTP Version Not Supported. The HTTP version used in the request is not supported by the server.

Question 51

511 status code?

Answer 51

Network Authentication Required. The 511 status code indicates that the client needs to authenticate to gain network access.