The codes of this group inform that the server has accepted the request and will process it.
The server accepted the request and is satisfied with the initial information. The processing will continue.
101 Switching Protocols
The server approved the protocol switch requested by the user. The code is used when the server offers to upgrade to a new version of HTTP. Available protocols will be listed in the Update field, the user can select one of them.
The server signals that it has accepted the request, but it takes longer to process. The client does not need to close the connection, it must reset the timer and wait for the next command.
Success codes for request processing
The group codes indicate that the request has been accepted and successfully processed.
This is one of the most popular answers, it means that the request was accepted and successfully processed, the page is open and available for viewing. All pages to be indexed must return a 200 OK code.
A response means that the server accepted the request, processed it, and created a new resource. The code can be seen, for example, if the user created a new page. If it is impossible to create a new resource, or it will cease to exist by the time the client receives the message, the server will return the 202 Accepted code.
The server accepted the request but did not complete its processing. The request may be rejected because it may take too long to complete.
203 Non-Authoritative Information
The response code 203 means that the operation was successful, but it differs from the code 200 in indicating the source of the information. The data was not obtained from the original source, but from another server or backup. Perhaps the information is out of date, which is what the response code warns about.
204 No Content
The request was processed successfully, but the server has nothing to send back. The response does not contain the body of the message, only the headers. Typically, this code is included in the first blank line of code to allow scripts to run without changing content or refreshing the page.
205 Reset Content
The server signals that the request has been successfully processed and the client needs to discard the entered data. Updating the document is not required, the server does not transmit the body of the message.
206 Partial Reset
This code is commonly used by caching tools. In response, the server returns only part of the page content that the user requests.
The code denotes a multi-status response: the server has processed several operations that do not depend on each other. The results are displayed in the body of the message as an XML document with a multistatus object.
226 IM Used
The server completed the operation successfully: it received the A-IM header and returned the content with the specified parameters.
The class of codes shows that in order to successfully complete the request, the client needs to make a transition, that is, a redirect.
300 Multiple Choices
The robot cannot index the page because it cannot match the resource and the URL. A common reason is that the resource has been moved to a different address. The server offers the client a choice of alternatives for the transition. For successful indexing, you need to either specify the resource correctly, or correct the headers.
301 Moved Permanently
If the address of the indexed page has changed, then a 301 redirect is set up from the old URL to the new one. The response code indicates that the requested document has been permanently moved to another URL, where the user is being redirected to by the link. The robot will index the page to which the redirect leads, and glue the original address and the new one.
The code means not permanent, but temporary movement of the page to a different address, so there is no need to remove the page from the index. The response indicates the new location of the data.
The page remains in the index, the link weight continues to be transmitted.
303 See Other
The server signals that the resource specified in the request is located at a different address. Typically it is used to redirect the user to the selected resource by outputting the data from a POST-activated script.
The server response will indicate the address where you need to search for a result that satisfies the request.
304 Not Modified
It is recommended to issue the code if the page has not changed since the last visit by the robot. The server signals this to the bot, the bot receives http headers from the document without reloading the page, which makes indexing faster and reduces the load on the server.
305 Use Proxy
The response code is related to data security. The server issues a 305 code if access to the resource requested by the client is possible only with a proxy. The proxy is indicated there in the server response.
307 Temporary Redirect
Code 307 is similar to 302, but gives a more specific answer. The code means that the resource requested by the client has been temporarily transferred to a different address, and the new URL must be written to Location.
Client error codes
The response codes of this group mean errors due to the fault of the client or the inability to return a result, because there is no data on the page.
400 Bad Request
The request is incorrect, somewhere in it there is a syntacticerror, so the server cannot return a result. For the successful execution of the request, you need to correct the syntax, usually clearing the cookies or page cache, correcting the request by the user helps.
The information is available only to registered users or password protected. If the user is not logged in, the page cannot be accessed.
The request was successfully received and correctly formulated, but the server does not have access to the requested page. It is possible that access is restricted specifically to certain IP addresses using the .htaccess file.
If the user www-data, under which the server is running, is denied access to read the file, the command sudo chmod o = r /usr/share/nginx/html/index.html will help
Another reason is that the user has accessed a closed directory that does not contain an index file. Permission to view the directory is enabled in the server settings.
404 Not Found
The server could not find the resource requested by the user, the document does not exist at this address.
This is a common error, it may be due to the fact that the user made a mistake in the page address, the user does not have permission to read and execute the file, the file on the server was moved or deleted, the root directory was specified with an error, or the server is not configured to work with symbolic "soft "links used for processing.
check server response code
404 Not Found response code
Links to remote sections of the site will return a 404 code. There is no need to spend crawling budget on such documents, so the robots.txt file prohibits the robot from visiting and indexing such pages.
405 Method Not Allowed
The method by which the request is made is not available. The server issues this code for specific individual objects on the page. For example, the query string that runs the script is different from the query that the user makes.
406 Not Acceptable
The response code means that the requested file exists, the request is formulated correctly, but the encoding of the document is not available for decryption by the robot.
407 Proxy Authentication Required
This code is similar to 401 and 407, it is used if the question is correct, but the client can only access the document using proxy authentication. The client is authorized if the proxy returns a field with the proxy-authenticate header.
408 Request Timeout
The server returns this response code if the client did not make any requests within the specified timeout. The 408 code is not returned if the user canceled the request himself, or the connection was dropped and there is no way to send a response.
The code means that there is a conflict in the system: for example, a user uploads a file to a server where there is already such a file in the new version.
The response code is similar to the 404 code, it means that the document to which the request is directed is no longer available. If the server returns a 404 code, then the robot will still return to the page to check its status, and in case of a 410 response, the robot will understand that the page has been deleted forever.
411 Length Required
The server cannot accept and process the request if the content-length is not specified in the content-length header.
413 Request Entity Too Large
If the request body contains too much information and the server cannot process such a large request, then it returns error code 413. If this is a temporary problem, the server will indicate the time to wait in the Retry-After field.
414 Request-URL Too Long
Likewise with code 413, except that the 414 code is displayed if the request contains a too long URL.
422 Unprocessable Entity
The server returns this code if it has accepted and recognized the request, but there is a logical error in the request body that prevents it from being executed.
424 Failed Dependency
If the execution of this operation depends on the outcome of other related operations, the server will return this request.
429 Too Many Requests
Code 429 means that the user is sending too many requests in a short period of time, and the server cannot handle that many.
431 Request Header Fields Too Large
If the request contains too large header fields, the server will not be able to cope with such a request and will return error code 431.
451 Unavailable For Legal Reasons
The code displays the same as 403, but with clarifications. It is used if access to the server is blocked by a court order, usually due to copyright infringement, or if access is denied at the state level.
418 I'm a teapot
This funny code that returns the "I'm a kettle" error is related to the Hyper Text Coffee Pot Control Protocol. An error means that the request is incorrect, the kettle cannot be used to make coffee. The protocol and the code for this error were created as a joke in 1998 by April 1st.
Code 418 I'm a teapot
Server error codes
Codes in this group indicate server-side errors.
500 Internal Server Error
The code indicates that the server cannot process the request due to internal errors. Usually the problem is with the server setup, accessing an invalid .htaccess file, or a PHP package that is not installed.
The server returns this code when it cannot process the request: it does not support processing capabilities, or it cannot recognize the method. For example, this error will appear if the common protocols HEAD, POST, GET and others are not supported by the server for some reason.
502 Bad Gateway
The backend servers are responsible for processing the request and transmit data to the proxy server or gateway. If the request was directed to a gateway that did not receive a response from the backend, the server will return a 502 code. To fix it, you need to check the proxy server setting.
503 Service Unavailable
The code indicates that the server is overloaded, the request cannot be completed at the moment. The second reason could be server maintenance: it does not have enough memory or resources to process the request. This response can be returned if the number of users is limited on the server.
504 Gateway Timeout
The code is similar to 502, but a 504 error means the server timed out. The required amount of time has elapsed and no response has come from the backend server.
This could be due to the network connection, lack of resources, the version of the HTTP protocol, or the setting of the server if the timeout is set too short.
506 Variant Also Negotiates
The response code 506 means that the server is configured incorrectly: an error in the configuration loops the server's call, and it points to itself.
507 Insufficient Storage
If the server is so loaded that there is not enough memory to fulfill the request, it will return a 507 error. This happens if there is no room on the server for data in the received request.
510 Not Extended
Code 510 is returned if the server does not support the extension specified in the request. In the same response, the server can indicate which extensions are available.
511 Network Authentication Required