What are HTTP status codes

HTTP status code is a three-digit integer code used to indicate whether a specific HTTP request has been successfully completed, indicating the HTTP response status; the first number of the code defines the type of server response, and the following two numbers have no classification. .

Types of HTTP status codes

HTTP status codes can be divided into five categories, consisting of The first digit of the status code represents the different categories:

1xx Class: Information

1xx class code indicates that the request has been received and the process is continuing. If HTTP status code 1xx is sent, the server notifies the client that the request is in motion. This class combines the code responsible for delivering information to the client during a request.

2xx class: Success

2xx class code indicates that the client's request has been successfully received and run. If this code is transmitted, it means that the client's request has been received, understood, and accepted by the server. It is usually sent at the same time as the desired website information, and users usually only pay attention to the website they requested.

3xx class: Redirect

3xx class code indicates that a request from the server has been received, but in order to ensure that the request is successfully processed, further steps are required from the client. 3xx codes will appear during redirection and forwarding.

4xx Class: Client Error

4xx class code indicates that the request contains incorrect syntax or that the request cannot be fulfilled, that is, there is a client error. The server received the request but was unable to execute it. Internet users will be aware of this error by receiving automatically generated HTML pages.

5xx class: Server error

4xx class code indicates that the server has an error or abnormal state during the process of processing the request, causing the server to be unable to execute the request. . These server error codes report that the request cannot be performed currently or at all, which results in an HTML error page.

Top 10 HTTP status codes

200: OK

indicates that the request was successful. The meaning of success depends on the HTTP method:

GET method: Indicates that the resource has been obtained and transmitted in the message body.

HEAD method: Indicates that the entity header is located in the message body.

PUT or POST method: Indicates that the resource describing the operation result is transmitted in the message body.

TRACE method: Indicates that the message body contains the request message received by the server

201: Create

Indicates that the request was successful and a new resource was created . This is usually a response sent after a POST request or after some PUT request.

204: No content

Indicates that the request has been successfully processed, but no content body was returned.

304: Unmodified

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.

400: Bad Request

400 is a generic client error status, used when no other 4xx error codes apply. Errors may resemble malformed request syntax, invalid request message parameters, or deceptive request routing, etc. It means that the server cannot understand the request due to invalid syntax.

401: Unauthorized

The 401 error response indicates that the client is trying to run on a protected resource without providing appropriate authorization. It may have provided incorrect credentials. Or not at all. Semantically it means "unauthenticated". That is, the client must authenticate itself to get a response to the request.

403: Forbidden

The 403 error response indicates that the client's request was correctly formed, but the REST API refused to recognize it, i.e. the user does not have the necessary permissions to the resource (without authorization), so the server refuses to provide an appropriate response. Unlike 401, the server knows the client's identity.

404: Not Found

The server cannot find the requested resource. In the browser, this means that the REST API cannot map the client's URI to the resource, but it may be available in the future; it also means that the endpoint may be valid but the resource itself does not exist.

404 is probably the most famous error status code because it appears so often on the web.

500: Internal Server Error

500 is a generic REST API error response and is a collected status code that should be applied to unexpected server errors. This HTTP status code is automatically issued if an error occurs on the server side (which prevents retrieval of the requested data).

504: Gateway Timeout

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

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