Learn HTTP Status Codes

30 Jul 2020 ⏱️ 6 min

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HTTP Status codes are 3-digit numbers which specify the status of whether a particular HTTP request was completed or not. These codes are a part of header in response.

These codes are not part of site content but rather are a way of informing the client about the status of request sent to server. It is important for any developer to learn about HTTP status codes since proper error codes are super useful in debugging applications. Incorrect HTTP codes lead to confusion, these are set of defined standard codes which are followed all over web.

You probably would have seen 400 Page not found or 500 internal server error while browsing the web. These are some of the HTTP response status codes.

In this article, we will be exploring various types of HTTP status codes and understand when and where to use which code.

Types of HTTP Status Codes

There are five different groups which contain few response status code. The first digit in the 3-digit code represents the class/group of HTTP status code. The five groups are -

Informational responses - 1xx [100–199]
Successful responses - 2xx [200–299]
Redirects - 3xx [300–399]
Client errors - 4xx [400–499]
Server errors - 5xx [500–599]

Let’s explore each of them in detail -

Informational Responses - 1xx 📘

Code	Description	Explanation
100	Continue	Client should continue with the request. Some part of the request has been received by the server, but as long as it has not been rejected, .
101	Switching Protocols	Client has asked the server to switch protocols and the server acknowledges with code

Successful responses - 2xx ✔️

Code	Description	Explanation
200	OK	The request is successful. The response depends on HTTP Methods - GET, POST, etc.
201	Created	New resource created and successful response.
202	Accepted	The request has been accepted for processing, but the processing has not been completed.
203	Non-Authoritative Information	Information in header is from a local/third-party copy, not from the original server.
204	No Content	Response has status code and header but not body.
205	Reset Content	This response requires that the requester reset the document view.
206	Partial Content	Server is returning partial data of the size requested defined by Range header

Redirects - 3xx 👉

Code	Description	Explanation
300	Multiple Choices	More than one possible response. Client chooses one of them.
301	Moved Permanently	The requested page has moved to a new url. All future request should be made at new url.
302	Found	Requested resource resides temporarily under a different url.
303	See Other	Server directs the client to get the requested resource at another url.
304	Not Modified	Response has not been modified, use the cached version.
305	Use Proxy	Requested resource MUST be accessed through the proxy given by the Location field
307	Temporary Redirect	Client should continue to use the Request-URI for future requests.

Client errors - 4xx ❌

Code	Description	Explanation
400	Bad Request	Server could not understand the request due to invalid/malformed syntax.
401	Unauthorized	Client should authenticate itself to get the requested response.
402	Payment Required	Reserved for future
403	Forbidden	Client does not have access rights to the content, even with authentication this request cannot be fulfilled.
404	Not Found	Server cannot find the requested page.
405	Method Not Allowed	HTTP method in request is not allowed.
406	Not Acceptable	Server is capable of generating only content that is not acceptable by client as specified in header.
407	Proxy Authentication Required	Authentication is required to be done by a proxy.
408	Request Timeout	Server timed out. It did not receive request from client within specific time.
409	Conflict	The request could not be completed due to a conflict with the current state of the resource
410	Gone	Requested page is no longer available. Similar to 404 but this is permanent.
411	Length Required	Server requires `Content-Length` header.
412	Precondition Failed	Precondition given in some request-header fields evaluated to false when it was tested on the server.
413	Request Entity Too Large	Request is too large for server to process.
414	Request-URI Too Long	Query string that is too large for the server to process.
415	Unsupported Media Type	Entity of the request is in a format not supported by the requested resource.
429	Too many request	Server cannot process these many request in given time. (Rate limiting)

Server errors - 5xx 🔻

Code	Description	Explanation
500	Internal Server Error	Server has met unexpected condition which has caused an error.
501	Not Implemented	Server doesn’t support the functionality required to fulfill the request.
502	Bad Gateway	Server has received an invalid response from the another resource(eg. third party payment request) thus request cannot be fulfilled.
503	Service Unavailable	Server is overloaded or currently down.
504	Gateway Timeout	Gateway did not get response in time.
505	HTTP Version Not Supported	HTTP version used in the request is not supported by the server.