The HTTP status code is composed of 3 decimal numbers . The first decimal number defines the type of status code. There are five categories in total. The detailed description of each status code is as follows:
| type | A detailed description |
|---|---|
| 100–199 | Information response, the server receives the request, and the requester needs to continue to perform the operation |
| 200–299 | A successful response, the operation was successfully received and processed |
| 300–399 | Redirected, further action is required to complete the request |
| 400–499 | Client error, the request contained syntax errors or could not be completed |
| 500–599 | Server error, the server encountered an error while processing the request |
Common HTTP status codes:
| status code | A detailed description |
|---|---|
| 200 - OK | Indicates that the request sent from the client to the server was processed normally and returned |
| 204 - No Content | Indicates that the request sent by the client to the client has been successfully processed, but the body part of the entity is not included in the returned response message (no resource can be returned) |
| 206 - Patial Content | Indicates that the client has made a range request, and the server has successfully executed this part of the GET request, and the response message contains the entity content of the range specified by Content-Range |
| 301 - Permanent Redirect | A permanent redirect, indicating that the requested resource was assigned a new URL, and the changed URL should be used afterwards |
| 302 - Temporary redirect | For explicit redirection, the value of the Location response header is the new URL. |
| 304 - Not Modified: not modified | For example: when comparing the resource files cached locally with those on the server, it is found that there is no modification, and the server returns a 304 status code, telling the browser that you do not need to request the resource, but just use the local resource directly |
| 400 - Bad Request | The client request has a syntax error and cannot be understood by the server |
| 401 - Unauthorized | Without permission, HTTP authentication is required. The sent request needs to have authentication information that passes HTTP authentication (BASIC authentication, DIGEST authentication). If a request has been made before, it means that the user authentication failed. Responses returned with a 401 MUST include a WWW-Authenticate header applicable to the requested resource to challenge user information. When the browser receives a 401 response for the first time, a dialog window for authentication will pop up. |
| 402 - Payment Required | Reserved for digital payment systems. However, it is not widely used. |
| 403 - Forbidden | The client request was denied because the client does not have permission to access the content. Unlike 401, the server knows the identity of the client, but since they don't have permission to view the content, the server refuses to provide a proper response |
| 404 - Not Found | The requested resource (webpage, etc.) does not exist, such as: wrong URL |
| 500 - Internal Server Error | Internal server error, such as: the data format transmitted by the front end does not match the data format required by the back end, and 500 will be reported |
| 502 - Bad Gateway | The proxy server cannot contact the backend server |
| 503 - Server Unavailable | The server is currently unable to process the client's request and may return to normal after a period of time |
| 504 - Gateway Timeout | The proxy can contact the backend server, but the backend server does not respond to the proxy server within the specified time |