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To help you identify what each HTTP status code is, below is a list that summarizes the Wikipedia:

Category 1xx – Informational
This status code class indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line. Since HTTP/1.0 does not define all 1xx status codes, servers should not send a 1xx response to an HTTP/1.0 client except under experimental conditions.

  • 100 Continue
    This means that the server has received the request headers, and the client must proceed to send the request body (in the case of a request for which a body must be sent, for example, a POST request). If the request body is large, sending them to a server when the request has already been rejected based on inappropriate headers is inefficient. To have a check from the server whether the request can be accepted based on the request headers alone, the client must send Expect: 100-continue as a header in its initial request and verify that a 100 Continue status code is received in response before standing (or receive 417 Expect Failed and not continue).
  • 101 Changing protocols
    This means that the requester has asked the server to change protocols and the server is acknowledging that it will do so. 102 Processing (WebDAV) (RFC 2518) Because a WebDAV request may contain many sub-requests that involve file operations, it may take a long time to complete the request. This code indicates that the server has received and is processing the request, but no response is yet available. This prevents the customer from timing out and assuming that the order was lost.
  • 122 Request-URI too long
    This is an IE7 standard code only does not mean the URI is more than a maximum of 2083 characters. (See code 414).

Category 2xx – Success
This class of status codes indicates the action requested by the client was successfully received, understood, accepted, and processed.

  • 200 OK
    Response pattern for successful HTTP requests. The actual response will depend on the request method used. In a GET request, the response will contain an entity that matches the requested resource. In a POST request the response will contain the description of an entity, or containing the result of the action.
  • 201 Created
    The request was fulfilled and resulted in a new resource being created.
  • 202 Accepted
    The request was accepted for processing, but the processing was not completed. The request may or may not be put into practice, as it may be canceled when processing actually takes place.
  • 203 unauthorized (since HTTP/1.1)
    The server processed the request successfully, but is returning information that could be from another source.
  • 204 No content
    The server processed the request successfully, but is not returning any content.
  • 205 Reset
    The server processed the request successfully, but is not returning any content. Unlike the 204, this response requires the requester to reset the document view.
  • 206 Partial content
    The server is only delivering part of the resource due to a header range sent by the client. The range header is used by tools like wget to allow resuming interrupted downloads, or splitting a download into multiple simultaneous streams.
  • 207-Multi-Status (WebDAV) (RFC 4918)
    The following message body is an XML message and may contain a number of individual response codes, depending on how many sub-requests were made.

Category 3xx – Redirection
The customer must take additional steps to complete the order. This status code class indicates that action still needs to be taken by the user agent in order to fulfill the request. The required action can be performed by the agent, without interaction with the user, if and only if the method used in the second request is GET or HEAD. A user agent should not automatically redirect a request more than five times, since such redirects often indicate an infinite loop.

  • 300 Multiple choice
    Indicates multiple options for the resource that the customer can track. It, for example, could be used to present different format options for video, list files with different extensions, or word sense disambiguation.
  • 301 Moved
    This and all future requests must be directed to the URI.
  • 302 Found
    This is an example of good industrial practice contradicting the norm. The HTTP/1.0 specification (RFC 1945) required the client to perform a temporary redirect (the original phrase describing it was “Moved Temporarily”), but popular browsers performed 302 with the functionality of a 303 See Others. Therefore, we added HTTP/1.1 status codes 303 and 307 to distinguish between the two behaviors. However, most web applications and frameworks still use the 302 status code as if it were 303.
  • 304 Not modified
    Indicates that the resource has not been modified since the last request. Typically, the client provides an HTTP header such as the If-Modified-Since header to provide a time against which to compare. Using this saves bandwidth and reprocessing on the server and client since only the header data must be sent and received compared to the entire page being reprocessed by the server then sent again using more server and client bandwidth.
  • 305 Use Proxy (since HTTP/1.1)
    Many HTTP clients (such as Mozilla and Internet Explorer) may not correctly handle responses with this status code, mainly for security reasons.
  • 306 Proxy Switch
    It stopped being used.
  • 307 Temporary redirect (since HTTP/1.1)
    On this occasion, the request must be repeated with another URI, but future requests may still use the original URI. In contrast to 303, the ordering method must not be changed when reissuing the original order. For example, a POST request must be repeated with another POST request.

Category 4xx – Client error
The 4xx class of status code is intended for cases where the client appears to have made an error. Except when responding to a HEAD request, the server must include an entity that contains an explanation of the error situation, and whether it is a temporary or permanent condition. These status codes are applicable to any request method. User agents must display any added entities to the user. These are typically the most common error codes encountered while online.

  • 400 Invalid request
    The order cannot be delivered due to incorrect syntax.
  • 401 Unauthorized
    Similar to 403 Forbidden, but specifically for use when authentication is possible but unable or not yet provided. The response must include a www-authenticat field header containing a challenge applicable to the requested resource. See Basic access authentication and Digest access authentication.
  • 402 Payment required
    Reserved for future use. The original intention was that this code could be used as part of some form of digital cash or micropayment scheme, but this did not happen, and this code is not commonly used.
  • 403 Forbidden
    The request was a legal request, but the server is refusing to respond to it. Unlike an Unauthorized 401 response, authentication will make no difference.
  • 404 Not found
    The requested resource was not found, but may be made available again in the future. Subsequent requests by the client are permitted. Occasionally, the requested resource has been removed from the server for some reason, but it can be replaced if necessary.
  • 405 Method not allowed
    A request was made for a resource using a request method that is not compatible with that resource, for example, using GET on a form, which requires the data to be presented via POST, PUT, or use in a read-only resource.
  • 406 Not Acceptable
    The requested resource is only capable of generating unacceptable content according to the Accept headers sent in the request.
  • 407 Proxy authentication required
  • 408 Request Timeout
    The server suffered a timeout while waiting for the request. According to the HTTP W3 specifications: "The client does not submit a request within the time that the server was prepared to wait for the time. The client may repeat the request without modifications at any time."
  • 409 Conflict
    Indicates that the request could not be processed because of a conflict in the request, such as an edit conflict.
  • 410 Gone
    Indicates that the requested resource is no longer available and will not be available again. This should be used when a resource was intentionally removed and resources must be removed. Upon receiving a 410 status code, the customer should not request the resource again in the future. Clients such as search engines must remove the resource from their indexes. Most use cases do not require clients and search engines to purge the resource, and a “404 Not Found” can be used.
  • 411 required length
    The request does not specify the length of its content, which is required by the requested resource.
  • 412 Precondition failed
    The server does not fulfill one of the conditions that the requester places in the request.
  • 413 Request entity too large
    The request is larger than the server is willing or able to process.
  • 414 Request-URI Too Long
    The URI provided was too long for the server to process.
  • 415 Unsupported media type
    The entity has a requested media type that the server or resource does not support. For example, the client loads an image as image/svg+xml, but the server requires that images use a different format.
  • 416 Unsatisfactory Range Request
    The client requested a part of the file, but the server cannot provide that part. For example, if the customer requested a part of the file that is beyond the end of the file.
  • 417 Expectation failure
    The server cannot meet the requirements of the Wait-Request header field.
  • 418 I am a teapot
    This code was defined in 1998 as one of the IETF's traditional April Fools jokes, in RFC 2324, Hyper Text Coffee Maker Control Protocol, and is not expected to be implemented by real HTTP servers.
  • 422 Unprocessable Entity (WebDAV) (RFC 4918)
    The request was well formed, but was unable to be followed due to semantic errors.
  • 423 Closed (WebDAV) (RFC 4918)
    The resource being accessed is blocked.
  • 424 Dependency Failure (WebDAV) (RFC 4918)
    The request failed because a previous request (for example, a PROPPATCH) failed.
  • 425 Unordered Collection (RFC 3648)
    Defined in “WebDAV Advanced Collections Protocol” projects, but not present in the “Web Distributed Authoring and Versioning (WebDAV) Sorted Collections Protocol”.
  • 426 Mandatory Upgrade (RFC 2817)
    The client must switch to another protocol, such as TLS/1.0 . Answer #444 An Nginx HTTP server extension. The server returns no information to the client and closes the connection (useful as a deterrent to malware). Com 449 Repeat A Microsoft extension. The request must be repeated after performing the appropriate action.
  • 450 blocked by Windows Parental Controls
    An extension of Microsoft. This error is given when Windows Parental Controls are activated and are blocking access to a certain web page.
  • 499 customer closed Order (used in ERPs/VPSA)
    An Nginx HTTP server extension. This code is introduced to record the case when the connection is closed by the client to the HTTP server is processing its request, causing the server to be unable to send the HTTP header back.

Category 5xx – Other errors

  • 500 Internal Server Error
    Indicates a server error processing the request. In the vast majority of cases, it is related to the permissions of the files or folders of the software or script that the user tries to access and were not configured when programming/building the website or application. To correct this, check the directory where the file or resource that failed to access is located, and this file (AS WELL AS ALL OTHERS), obey the following rules:
    Folders — chmod 755 (do not use 777)
    Files — chmod 644 (do not use 777, only use another if expressly requested during installation)

    NOTE: some applications and/or systems require different permissions, which is why it is important to check with the creators of the scripts/system, which would be the correct permission to use. The example describes how it is performed on Unix-like operating systems. Make an analogy to how it is done in systems like Windows (Windows 7, 8, XP among others).

    This error can also occur if the file. Htaccess of your website You are trying to modify the parameters using PHP as commands: php_flag or php_value. Remove any entries with these commands from the .htaccess file. If you are going to make changes to the PHP parameters, use the php.ini file to do this.

  • 501 Not implemented
    The server does not yet support the enabled functionality
  • 502 Bad Gateway
    Typically, the error occurs when there is an inaccurate configuration between the back-end computers, possibly including the web server on the visited website. Before analyzing this problem, you need to clear your browser cache completely. If you are surfing the web and notice this problem on every website you visit, then 1) your Internet service provider has a major equipment failure/overload or 2) there is something wrong with your internal Internet connection, for example, the firewall is not working properly. If it's the first case, only your provider can help. If it's the latter, you need to fix whatever is preventing you from accessing the Internet. If you only experience this problem on some websites you visit, there is probably a problem with those websites. For example, one of the pieces of equipment is failing or is overloaded. Contact those responsible for these sites.
  • 503 Service Unavailable
    The server is undergoing maintenance or cannot handle resource processing due to system overload. This should be a temporary condition.
  • 504 Gateway Time-Out
    It is characterized by errors particular to the website in question. It may be that the website is under maintenance or does not exist.
  • 505 HTTP Version not supported
    Most browsers assume that network servers support versions 1.x of the HTTP protocol. In practice, very old versions like 0.9 are little used today, not just because they provide little security and lower performance than newer versions of the protocol. So, if this error occurs in your web browser, the only option is to upgrade the web server software. If the request version 1.x fails, it may be because the network server is supporting incorrect versions of the 1.x protocol, rather than not supporting them at all.