Understanding Http Status Codes

By on August 4th, 2016

We all are familiar with web browsers. While accessing the Internet, sometimes we will be getting error pages such as “Page not found”, “Internal Server Error” etc. These error messages contain a code. These are known as http status codes. Being the error, it is actually the status of the http request, so that is called, status codes.


Structure of http status codes

The http status codes element is a three-digit integer. The first digit of the code defines the class of the server response and the following two digits are not having any classification. There are five values for the first digit. They are given below.

1XX: Informational


2XX: Success


3XX: Redirection


4XX: Client Error

It means the request contains incorrect syntax or the request cannot be fulfilled.

5XX: Server Error

It means that the server failed to fulfil an apparently valid request. Even though there are a vast number of http status codes, it is not required to know all the status codes for successful internet access.


The top 10 http status codes are given below.

200 OK

201 Created

204 No Content

400 Bad Request

401 Unauthorized

403 Forbidden

404 Not Found

409 Conflict

500 Internal Server Error

As the above are the status codes, the class 4XX is known as the client error. Let us discuss about common client error status codes and what do they mean. In the list above, there are five status codes which are very common to us.


400 Bad Request

The first status code we are going to see is 400 Bad Request. It means that the request could not be understood by the server due to malformed syntax. The client should not repeat this request without modifications. It states that the request cannot be fulfilled due to poor syntax. It is the common error that returns when fulfilling the request cause an invalid state. Domain validation errors and missing data are examples for kind of errors.
401 Unauthorized

This status code comes when the request requires user authentication. This is the error code response for missing or invalid authentication token. It is similar to 403 forbidden error, but specifically used when authentication is possible, but failed or not provided yet. The 403 forbidden error means that the server is refusing to fulfill the request even if the authentication is provided. The response must contain a WWW-. Authenticate header field contains a challenge which is applicable to the requested resource.

In this case, the user may repeat the request with a suitable Authorization header field. If the request already contains authorization credentials, this response indicates that authorization has been refused for those credentials.


403 Forbidden

This is another error that is familiar to most of us. This status code is the one when the user is not authorized to perform the operation or the resource is unavailable for some reason. Normally this occurs when the server understood the request and is refusing to fulfill it. In this case, the authorization will not be helpful and the request should not be repeated. If the request method was not head and the server wants to make it public that why the request has not been fulfilled, it should describe the reason for the particular refusal in the entry. If the server does not wish to make it public, which means the server does not wants to make this information available to the client, the status code, 404 not found can be used instead of 403 forbidden.

This is actually not like the 401 unauthorized response, because, the request is a legal request and authenticating will make no difference. That is the main difference between 401 unauthorized and 403 forbidden status codes.


404 Not Found

This is the most common http status code in our experience. This the error code stands for when the requested webpage is not found on the specified server. This error code returns when the server has not found anything matching the requested URL. There can be various situations that may leads to this error. The requested webpage doesn’t exist or if there was a 401 unauthorized or 403 forbidden. For security reasons, the service wants to mask the reason from the clients.

For the 404 not found status code, even though the requested resource could not be found, the resource may be available again in the future and subsequent requests from the client are permitted. There will not be any indication given regarding the condition is temporary or permanent. The 410 Gone status code is used when the server knows through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address.

This status code is commonly used when the server does not wish to reveal exactly why the request has been refused or when no other response is applicable. This is what the reason for 404 not found error.


500 Internal Server Error

The 5XX are server errors comes when the server encounters an unexpected condition which prevented it from fulfilling the request. It is the general catch-all error when the server-side throws an exception. It is the error message when no more specific message is suitable. It can be difficult to troubleshoot this error because many different issues can trigger this error. It is rare but not impossible that the problems with the computer that connects to the server to trigger this error. The scripting issues are the common cause of this error such as if a form fails to correctly handle a missing or incorrect value. This error can be because of the faults in server side. Also such as a failed disk or a non-functional software module.

These are the most common error codes or http status codes that we encounter in our daily life. It is good and very helpful that knowing what they actually mean when going through these status conditions.


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