preface
When a visitor visits a web page, the visitor’s browser makes a request to the server where the page is located. When the browser receives and displays a web page, the server where the web page resides returns a Server header containing an HTTP status code in response to the browser’s request.
Common status code
- 200 – Request successful
- 301 – Resources (web pages, etc.) are permanently transferred to another URL
- 404 – Requested resource (web page, etc.) does not exist
- 500 – Internal server error
HTTP status code classification
| Status code | category | describe | understand |
|---|---|---|---|
| 1XX | Information (Informational status code) | Message, the server receives the request and requires the requester to proceed with the operation | The received request is being processed |
| 2XX | Success (Success Status code) | Success, the operation is received and processed successfully | The request is successfully processed |
| 3XX | Redirection (Redirection status code) | Redirect, requiring further action to complete the request | Additional action is required to complete the request |
| 4XX | Client Error (Client Error status code) | Client error, request contains syntax error or request cannot be completed | The server cannot process the request |
| 5XX | Server Error | Server error. The server encountered an error while processing the request | The server failed to process the request |
Status code starting with 1 (temporary response)
- These status codes represent temporary responses. Clients should be prepared to receive one or more 1XX responses before receiving regular responses.
| Status code | describe | The English name |
|---|---|---|
| 100 | To continue. The client should continue with its request | Continue |
| 100 | Switch protocol. Protocols The server switches Protocols based on client requests. You can only switch to a more advanced protocol, for example, the new version of HTTP | Switching Protocols |
Status code starts with 2
- This type of status code indicates that the server successfully accepted the client request
| Status code | describe | The English name |
|---|---|---|
| 200 (Success) | The server has successfully processed the request. Typically, this means that the server has provided the requested web page. Typically used for GET and POST requests | OK |
| 201 (Created) | The request was successful and a new resource was created | Created |
| 202 (Accepted) | The server has accepted the request, but has not completed processing | Accepted |
| 203 (Unauthorized Information) | The server has successfully processed the request, but the meta information returned is not the original server, but a copy | Non-Authoritative Information |
| 204 (No content) | The server successfully processed the request, but did not return anything. | No Content |
| 205 (Reset content) | The server successfully processed the request, but did not return anything. You can ensure that the browser continues to display the current document without updating the web page | Reset Content |
| 206 (Part) | The server successfully processed some of the GET requests. | Partial Content |
Status code starting with 3
- Indicates that the browser needs to perform some special processing to properly process the request.
| Status code | describe | The English name |
|---|---|---|
| 300 (multiple options) | The server can perform a variety of actions on a request. The server can select an operation based on the requester (User Agent) or provide a list of operations for the requester to select. | Multiple Choices |
| 301 (Permanent move) | The requested page has been permanently moved to the new location. The requested resource has been permanently moved to the new URI, the return message will include the new URI, and the browser will automatically redirect to the new URI. Any future new requests should be replaced with a new URI | Moved Permanently |
| 302 (Temporary Removal) | The server currently responds to requests from web pages in different locations, but the requester should continue to use the original URL for future requests. | Found |
| 303 (View other locations) | Look at other addresses. Similar to 301. Use GET and POST requests to view | See Other |
| 304 (unmodified) | Unmodified. The requested resource is not modified, and the server does not return any resources when it returns this status code. Clients typically cache accessed resources by providing a header indicating that the client wants to return only resources that have been modified after a specified date | Not Modified |
| 305 (Using proxy) | The requester can only access the requested web page using a proxy. If the server returns this response, it also indicates that the requester should use a proxy. | Use Proxy |
| 307 (Temporary redirection) | The server currently responds to requests from web pages in different locations, but the requester should continue to use the original location for future requests. | Temporary Redirect |
Status code starts with 4
- These status codes indicate that the request may be in error, preventing the server from processing it.
| Status code | describe | The English name |
|---|---|---|
| 400 (Error request) | Client request syntax error, server cannot understand | Bad Request |
| 401 (Unauthorized) | The request requires user authentication. The server may return this response for a web page that requires login. | Unauthorized |
| 403 (Forbidden) | The server understands the request from the requesting client, but the server rejects the request. | Forbidden |
| 404 (Not found) | The server could not find the resource (web page) based on the client’s request. With this code, a web designer can set up a personalized page that says “the resource you requested could not be found. | Not Found |
| 405 (Method disabled) | The method in the client request is disabled | Method Not Allowed |
| 406 (Not accepted) | The server could not complete the request based on the content nature of the client request | Not Acceptable |
| 407 (Agency authorization required) | This status code is similar to 401 (unauthorized), but specifies that the requester should authorize the use of the agent | Proxy Authentication Required |
| 408 (Request timed out) | The server waited for a request sent by the client for a long time and timed out. Procedure | Request Time-out |
| 409 (Conflict) | This code may be returned when the server completes a PUT request from the client, and a conflict occurred when the server processed the request | Conflict |
| 410 (Deleted) | The resource requested by the client does not exist. 410 differs from 404 in that if a resource previously had a 410 code that is now permanently deleted, the site designer can specify a new location for the resource through the 301 code | Gone |
| 411 (Effective length required) | The server will not accept requests that do not contain a valid content-length header field. | Length Required |
| 412 (Conditions not met) | The server did not meet one of the prerequisites that the requester set in the request. | Precondition Failed |
| 413 (Request entity too large) | The request was rejected because the requested entity was too large for the server to process. To prevent continuous requests from clients, the server may close the connection. If the server is temporarily unable to process it, a retry-after response is included | Request Entity Too Large |
| 414 (Request URI too long) | The request URI is too long (usually a url) for the server to process | Request-URI Too Large |
| 415 (Unsupported Media Types) | The format of the request is not supported by the requested page. | Unsupported Media Type |
| 416 (Request scope does not meet requirements) | If the page cannot provide the requested scope, the server returns this status code. | Requested range not satisfiable |
| 417 (not satisfied with expected value) | The server did not meet the requirements for the “expected” request header field. | Expectation Failed |
The status code starts with 5
- These status codes indicate that an internal error occurred while the server was trying to process the request. These errors may be server errors rather than request errors
| Status code | describe | The English name |
|---|---|---|
| 500 (Server internal error) | The server had an internal error and could not complete the request | Internal Server Error |
| 501 (not yet implemented) | The server did not support the requested functionality and could not complete the request | Not Implemented |
| 502 (Wrong gateway) | The server working as a gateway or proxy received an invalid response from the remote server when attempting to execute the request. For example, the server may return this code if it does not recognize the request method. | Bad Gateway |
| 503 (Service unavailable) | The server is currently unavailable (due to overloading or downtime for maintenance). Usually, this is a temporary state. | Service Unavailable |
| 504 (Gateway timeout) | The server acts as a gateway or proxy, but does not receive requests from the upstream server in time. | Gateway Time-out |
| 505 (HTTP version not supported) | The server does not support the HTTP protocol version used in the request. | HTTP Version not supported |