Mohit Khare
Mohit Khare
Product Engineer @ Gojek | Blogs about tech, productivity and life.

Learn HTTP Status Codes

Learn HTTP Status Codes

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 -

  1. Informational responses - 1xx [100199]
  2. Successful responses - 2xx [200299]
  3. Redirects - 3xx [300399]
  4. Client errors - 4xx [400499]
  5. Server errors - 5xx [500599]

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.

Resources

You can find browser compatibity data for status code here.

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