426 ошибка http

The server refuses to perform the request using the current protocol but might be willing to do so after the client upgrades to a different protocol.

The server MUST send an Upgrade header field in a 426 response to indicate the required protocol(s)¹.

Example:

HTTP/1.1 426 Upgrade Required
Upgrade: HTTP/3.0
Connection: Upgrade
Content-Length: 53
Content-Type: text/plain

This service requires use of the HTTP/3.0 protocol.

¹ Upgrade RFC7230 Section 6.7
Source: RFC7231 Section 6.5.15

426 CODE REFERENCES

Rails HTTP Status Symbol :upgrade_required

Symfony HTTP Status Constant Response::HTTP_UPGRADE_REQUIRED

.NET HttpStatusCode.UpgradeRequired

Rust http::StatusCode::UPGRADE_REQUIRED

Go http.StatusUpgradeRequired

Python 3.5+ http.HTTPStatus.UPGRADE_REQUIRED

Apache HttpComponents Core org.apache.hc.core5.http.HttpStatus.SC_UPGRADE_REQUIRED

Angular @angular/common/http/HttpStatusCode.UpgradeRequired

426 status code example

Here’s an example request and response for a 426 status code:

Request

GET /index.html HTTP/1.1
Host: www.example.com
Connection: keep-alive
Upgrade: TLS/1.0

Response

HTTP/1.1 426 Upgrade Required
Date: Wed, 14 Jul 2021 17:00:00 GMT
Server: Apache
Upgrade: TLS/1.0, HTTP/1.1
Connection: Upgrade
Content-Length: 73
Content-Type: text/plain; charset=utf-8

This server requires the use of a secure connection. Please upgrade to TLS/1.0.

What causes a 426 status code?

A 426 status code is caused when a client is attempting to upgrade a connection to a newer version of a protocol, but the server is refusing to do so.

This can happen for several reasons, including:

Incompatibility between the client and server versions of the protocol.
The server may not support the requested version of the protocol.
The server may be configured to only allow certain versions of the protocol to be used.
The server may be experiencing technical issues or undergoing maintenance that prevents it from upgrading the connection.

In any case, the client will need to determine the reason for the 426 error and take appropriate action to resolve it, such as updating to a compatible version of the protocol or contacting the server administrator for assistance.

How to troubleshoot a 426 status code

Here are some ways to troubleshoot this error:

Check for server configuration issues: The 426 status code occurs when the client requests an upgrade to a different protocol version, but the server can’t comply with it. In such a case, you can check the server configuration to ensure that it supports the requested protocol version. You can also check if the server is configured to support HTTP/1.1, which is required for protocol upgrades.
Check for client-side issues: The 426 status code can also occur if the client is sending incorrect or unsupported upgrade headers. In such cases, you can check the client-side code to ensure that it’s sending the correct headers and supporting the protocol version that it’s requesting.
Check for network issues: The 426 status code can also occur due to network connectivity issues. In such cases, you can check the network settings and ensure that the client and server are connected to the same network. You can also check for firewall or proxy settings that might be blocking the request.
Update software versions: If the server or client is outdated, it may not support the latest protocol version requested. In such cases, updating the server or client software to the latest version may resolve the issue.

By following the above troubleshooting steps, you can identify and resolve the issue that’s causing the 426 status code.

Additional resources

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Return to List of HTTP Status Codes

Источник

HTTP response status code 426 Update Required is a client error that is returned by the server to indicate that it is unwilling to process the request using the current protocol. It does not guarantee that it will do so after the client upgrades to a different protocol, although it may be willing to do so.

Usage

When the 426 Upgrade Required status code is received, the response includes an Upgrade response header field to indicate the required protocol(s).

This message is related to the 101 Switching Protocols message, which is sent in response to the client asking that the server Upgrade the connection.

Note

Search engines like Google will not index a URL with 426 Upgrade Required response status, and consequently, URLs that have been indexed in the past but are now returning this HTTP status code will be removed from the search results.

Example

In the example, the client requests a resource and the server responds with the 426 Upgrade Required error message because it only supports HTTP/2 and HTTP/3. The client upgrades the connection to HTTP/2 and in response, the server sends the 101 Switching Protocols informational response. At this point, the request is processed.

Initial request

GET /tech-news HTTP/1.1
Host: www.example.re

Initial response, will not process request with this protocol

HTTP/1.1 426 Upgrade Required
Upgrade: HTTP/2, HTTP/3
Connection: upgrade
Content-Type: text/html
Content-Length: 154

<html>
  <head>
    <title>Protocol Not Supported</title>
  </head>
  <body>
   <p>This service supports HTTP/2 and HTTP/3 only.</p>
  </body>
</html>

Subsequent request, specifying protocol upgrade

GET /tech-news HTTP/1.1
Host: www.example.re
Connection: upgrade
Upgrade: HTTP/2

Informational response

HTTP/1.1 101 Switching Protocols
Upgrade: HTTP/2
Connection: upgrade

Code references

.NET

HttpStatusCode.UpgradeRequired

Rust

http::StatusCode::UPGRADE_REQUIRED

Rails

:upgrade_required

http.StatusUpgradeRequired

Symfony

Response::HTTP_UPGRADE_REQUIRED

Python3.5+

http.HTTPStatus.UPGRADE_REQUIRED

Apache HttpComponents Core

org.apache.hc.core5.http.HttpStatus.SC_UPGRADE_REQUIRED

Angular

@angular/common/http/HttpStatusCode.UpgradeRequired

Takeaway

The 426 Update Required status code is a client error that is sent by the server when the client is using a protocol that it does not support. Subsequent requests may be processed if the protocol is upgraded.

What Is 426 Http Status Code?

The HTTP 426 status code is an upgrade-required error that occurs when the current protocol of a client does not meet the requirements of the server. In this case, the server refuses to perform a request unless the client upgrades its protocol. This specific HTTP status code was introduced in 2015 and became part of RFC 7231 – Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content. It signals that the requested resource must be accessed using a different protocol version than what is currently being used by the client.

In order for clients to upgrade their protocols, they need to send an Upgrade header field with their requests. The response from the server will then contain information about which protocol version is required for successful communication between them. If this requirement isn’t met, then a 426 http status code will be returned as an indication that said upgrade needs to take place before any further action can occur.

This particular error code has become increasingly important during recent years due to its ability to help ensure secure connections between users and web applications or services are established through use of up-to-date protocols. By denying access until these necessary upgrades have been made, it helps protect both sides from potential security issues associated with outdated versions of certain protocols.

Cause Of 426 Http Status Code Error

The 426 http status code error is caused by the client’s request not being able to be performed using the current protocol. This can often occur when a server responds with an upgrade header, indicating that switching protocols should take place in order for the request to be properly fulfilled. As such, if a user attempts to perform the request using the current protocol, they will receive this particular HTTP status symbol as an indication that it failed due to lack of compatibility between their browser and server configurations.

In some cases, simply upgrading your connection or attempting again may resolve the issue; however, this only works if both the client-side and server-side are compatible with each other. If either side does not support performing the request using the current protocol, then no amount of retrying will help unless one of them upgrades first.

Server Side Or Client Side Issue?

When it comes to solving the mystery of HTTP 426 status code errors, it is important to consider whether the issue lies on either the server side or client side. A key factor in determining this is whether an Upgrade Required response was sent by the server. If so, then a protocol upgrade is needed as part of the service that requires additional content length than what was provided in the request. In such cases, the server sends an HTTP response status code of 426 and refuses to perform any further action until a suitable upgrade has been made by the client.

On the other hand, if no Upgrade Required response has been issued, then there may be some other form of Client Error occurring which would explain why and how the error code appears. This could include issues with authentication credentials supplied by users or lack thereof; incorrect parameters being sent from clients; improper formatting of requests; etcetera. All these can result in an HTTP status code 426 message appearing when attempting to access certain webpages.

In order for one to determine exactly where and why this error occurs, they should look at both their own system setup as well as examine more closely what information is being requested between servers and clients during communication attempts. From here, they can begin debugging towards finding out what needs attention before continuing on with resolving this particular issue.

How To Fix 426 Http Status Code Error

In order to fix this issue, one must first identify if it is indeed a 426 HTTP status code error they are dealing with. If so, then they can look into upgrading their current software or web application framework to a more recent version that supports newer protocols. Furthermore, they should also check if any plugins on their system need updating in order to support these new protocols.

Once all these steps have been taken care of, it’s time to test the connection again – if no further errors occur, then you will know that your upgrade was successful and the connection can now flow smoothly once more! Transitioning into similar HTTP status codes of 426 may still reveal potential issues.

Example

An example of the communication flow between a client and server where the server responds with an “Upgrade Required” error code (426), along with the steps the client needs to take to fix the error:

The client initiates a request to the server to access a particular resource:

GET http://example.com/my-resource HTTP/1.1

The server receives the request and checks if the client is using an outdated protocol or version. If the protocol or version is outdated, the server responds with a 426 Upgrade Required error code and specifies the required protocol or version the client needs to upgrade to:

HTTP/1.1 426 Upgrade Required
Upgrade: HTTP/2.0
Connection: Upgrade
Content-Length: 67
Content-Type: text/plain

This resource requires an upgrade to HTTP/2.0 or higher protocol.

The client receives the 426 response and understands that it needs to upgrade to the specified protocol or version. The client should then modify its request to include the Upgrade header and the new protocol or version:

GET http://example.com/my-resource HTTP/1.1
Upgrade: HTTP/2.0
Connection: Upgrade

The server receives the modified request and upgrades the connection to the specified protocol or version, responding with the requested resource and an appropriate success status code.

Similar Http Status Codes To 426

The 426 status code shares some similarities with other related codes, such as 400 Bad Request and 403 Forbidden Errors. The former appears when there is something wrong in the syntax of the request coming from the user-agent, while 403 errors are sent when authorization fails. Depending on what exactly caused the issue with your web browser, you might be willing to try out different versions until you find one compatible with your system’s configuration settings.

All HTTP status codes by categories

Источник

From Wikipedia, the free encyclopedia

This is a list of Hypertext Transfer Protocol (HTTP) response status codes. Status codes are issued by a server in response to a client’s request made to the server. It includes codes from IETF Request for Comments (RFCs), other specifications, and some additional codes used in some common applications of the HTTP. The first digit of the status code specifies one of five standard classes of responses. The optional message phrases shown are typical, but any human-readable alternative may be provided, or none at all.

Unless otherwise stated, the status code is part of the HTTP standard (RFC 9110).

The Internet Assigned Numbers Authority (IANA) maintains the official registry of HTTP status codes.^[1]

All HTTP response status codes are separated into five classes or categories. The first digit of the status code defines the class of response, while the last two digits do not have any classifying or categorization role. There are five classes defined by the standard:

1xx informational response – the request was received, continuing process
2xx successful – the request was successfully received, understood, and accepted
3xx redirection – further action needs to be taken in order to complete the request
4xx client error – the request contains bad syntax or cannot be fulfilled
5xx server error – the server failed to fulfil an apparently valid request

1xx informational response

An informational response indicates that the request was received and understood. It is issued on a provisional basis while request processing continues. It alerts the client to wait for a final response. The message consists only of the status line and optional header fields, and is terminated by an empty line. As the HTTP/1.0 standard did not define any 1xx status codes, servers must not^{[note 1]} send a 1xx response to an HTTP/1.0 compliant client except under experimental conditions.

100 Continue: The server has received the request headers and the client should proceed to send the request body (in the case of a request for which a body needs to be sent; for example, a POST request). Sending a large request body to a server after a request has been rejected for inappropriate headers would be inefficient. To have a server check the request’s headers, a client must send Expect: 100-continue as a header in its initial request and receive a 100 Continue status code in response before sending the body. If the client receives an error code such as 403 (Forbidden) or 405 (Method Not Allowed) then it should not send the request’s body. The response 417 Expectation Failed indicates that the request should be repeated without the Expect header as it indicates that the server does not support expectations (this is the case, for example, of HTTP/1.0 servers).^[2]
101 Switching Protocols: The requester has asked the server to switch protocols and the server has agreed to do so.
102 Processing (WebDAV; RFC 2518): A WebDAV request may contain many sub-requests involving file operations, requiring a long time to complete the request. This code indicates that the server has received and is processing the request, but no response is available yet.^[3] This prevents the client from timing out and assuming the request was lost. The status code is deprecated.^[4]
103 Early Hints (RFC 8297): Used to return some response headers before final HTTP message.^[5]

2xx success

This class of status codes indicates the action requested by the client was received, understood, and accepted.^[1]

200 OK: Standard response for successful HTTP requests. The actual response will depend on the request method used. In a GET request, the response will contain an entity corresponding to the requested resource. In a POST request, the response will contain an entity describing or containing the result of the action.
201 Created: The request has been fulfilled, resulting in the creation of a new resource.^[6]
202 Accepted: The request has been accepted for processing, but the processing has not been completed. The request might or might not be eventually acted upon, and may be disallowed when processing occurs.
203 Non-Authoritative Information (since HTTP/1.1): The server is a transforming proxy (e.g. a Web accelerator) that received a 200 OK from its origin, but is returning a modified version of the origin’s response.^[7]^[8]
204 No Content: The server successfully processed the request, and is not returning any content.
205 Reset Content: The server successfully processed the request, asks that the requester reset its document view, and is not returning any content.
206 Partial Content: The server is delivering only part of the resource (byte serving) due to a range header sent by the client. The range header is used by HTTP clients to enable resuming of interrupted downloads, or split a download into multiple simultaneous streams.
207 Multi-Status (WebDAV; RFC 4918): The message body that follows is by default an XML message and can contain a number of separate response codes, depending on how many sub-requests were made.^[9]
208 Already Reported (WebDAV; RFC 5842): The members of a DAV binding have already been enumerated in a preceding part of the (multistatus) response, and are not being included again.
226 IM Used (RFC 3229): The server has fulfilled a request for the resource, and the response is a representation of the result of one or more instance-manipulations applied to the current instance.^[10]

3xx redirection

This class of status code indicates the client must take additional action to complete the request. Many of these status codes are used in URL redirection.^[1]

A user agent may carry out the additional action with no user interaction only if the method used in the second request is GET or HEAD. A user agent may automatically redirect a request. A user agent should detect and intervene to prevent cyclical redirects.^[11]

300 Multiple Choices: Indicates multiple options for the resource from which the client may choose (via agent-driven content negotiation). For example, this code could be used to present multiple video format options, to list files with different filename extensions, or to suggest word-sense disambiguation.
301 Moved Permanently: This and all future requests should be directed to the given URI.
302 Found (Previously «Moved temporarily»): Tells the client to look at (browse to) another URL. The HTTP/1.0 specification (RFC 1945) required the client to perform a temporary redirect with the same method (the original describing phrase was «Moved Temporarily»),^[12] but popular browsers implemented 302 redirects by changing the method to GET. Therefore, HTTP/1.1 added status codes 303 and 307 to distinguish between the two behaviours.^[11]
303 See Other (since HTTP/1.1): The response to the request can be found under another URI using the GET method. When received in response to a POST (or PUT/DELETE), the client should presume that the server has received the data and should issue a new GET request to the given URI.
304 Not Modified: Indicates that the resource has not been modified since the version specified by the request headers If-Modified-Since or If-None-Match. In such case, there is no need to retransmit the resource since the client still has a previously-downloaded copy.
305 Use Proxy (since HTTP/1.1): The requested resource is available only through a proxy, the address for which is provided in the response. For security reasons, many HTTP clients (such as Mozilla Firefox and Internet Explorer) do not obey this status code.
306 Switch Proxy: No longer used. Originally meant «Subsequent requests should use the specified proxy.»
307 Temporary Redirect (since HTTP/1.1): In this case, the request should be repeated with another URI; however, future requests should still use the original URI. In contrast to how 302 was historically implemented, the request method is not allowed to be changed when reissuing the original request. For example, a POST request should be repeated using another POST request.
308 Permanent Redirect: This and all future requests should be directed to the given URI. 308 parallel the behaviour of 301, but does not allow the HTTP method to change. So, for example, submitting a form to a permanently redirected resource may continue smoothly.

4xx client errors

404 error on Wikimedia

This class of status code is intended for situations in which the error seems to have been caused by the client. Except when responding to a HEAD request, the server should include an entity containing 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 should display any included entity to the user.

400 Bad Request: The server cannot or will not process the request due to an apparent client error (e.g., malformed request syntax, size too large, invalid request message framing, or deceptive request routing).
401 Unauthorized: Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided. The response must include a WWW-Authenticate header field containing a challenge applicable to the requested resource. See Basic access authentication and Digest access authentication. 401 semantically means «unauthorised», the user does not have valid authentication credentials for the target resource.; Some sites incorrectly issue HTTP 401 when an IP address is banned from the website (usually the website domain) and that specific address is refused permission to access a website.^{[citation needed]}
402 Payment Required: Reserved for future use. The original intention was that this code might be used as part of some form of digital cash or micropayment scheme, as proposed, for example, by GNU Taler,^[14] but that has not yet happened, and this code is not widely used. Google Developers API uses this status if a particular developer has exceeded the daily limit on requests.^[15] Sipgate uses this code if an account does not have sufficient funds to start a call.^[16] Shopify uses this code when the store has not paid their fees and is temporarily disabled.^[17] Stripe uses this code for failed payments where parameters were correct, for example blocked fraudulent payments.^[18]
403 Forbidden: The request contained valid data and was understood by the server, but the server is refusing action. This may be due to the user not having the necessary permissions for a resource or needing an account of some sort, or attempting a prohibited action (e.g. creating a duplicate record where only one is allowed). This code is also typically used if the request provided authentication by answering the WWW-Authenticate header field challenge, but the server did not accept that authentication. The request should not be repeated.
404 Not Found: The requested resource could not be found but may be available in the future. Subsequent requests by the client are permissible.
405 Method Not Allowed: A request method is not supported for the requested resource; for example, a GET request on a form that requires data to be presented via POST, or a PUT request on a read-only resource.
406 Not Acceptable: The requested resource is capable of generating only content not acceptable according to the Accept headers sent in the request. See Content negotiation.
407 Proxy Authentication Required: The client must first authenticate itself with the proxy.
408 Request Timeout: The server timed out waiting for the request. According to HTTP specifications: «The client did not produce a request within the time that the server was prepared to wait. The client MAY repeat the request without modifications at any later time.»
409 Conflict: Indicates that the request could not be processed because of conflict in the current state of the resource, such as an edit conflict between multiple simultaneous updates.
410 Gone: Indicates that the resource requested was previously in use but is no longer available and will not be available again. This should be used when a resource has been intentionally removed and the resource should be purged. Upon receiving a 410 status code, the client should not request the resource in the future. Clients such as search engines should remove the resource from their indices. Most use cases do not require clients and search engines to purge the resource, and a «404 Not Found» may be used instead.
411 Length Required: The request did not specify the length of its content, which is required by the requested resource.
412 Precondition Failed: The server does not meet one of the preconditions that the requester put on the request header fields.
413 Payload Too Large: The request is larger than the server is willing or able to process. Previously called «Request Entity Too Large» in RFC 2616.^[19]
414 URI Too Long: The URI provided was too long for the server to process. Often the result of too much data being encoded as a query-string of a GET request, in which case it should be converted to a POST request. Called «Request-URI Too Long» previously in RFC 2616.^[20]
415 Unsupported Media Type: The request entity has a media type which the server or resource does not support. For example, the client uploads an image as image/svg+xml, but the server requires that images use a different format.
416 Range Not Satisfiable: The client has asked for a portion of the file (byte serving), but the server cannot supply that portion. For example, if the client asked for a part of the file that lies beyond the end of the file. Called «Requested Range Not Satisfiable» previously RFC 2616.^[21]
417 Expectation Failed: The server cannot meet the requirements of the Expect request-header field.^[22]
418 I’m a teapot (RFC 2324, RFC 7168): This code was defined in 1998 as one of the traditional IETF April Fools’ jokes, in RFC 2324, Hyper Text Coffee Pot Control Protocol, and is not expected to be implemented by actual HTTP servers. The RFC specifies this code should be returned by teapots requested to brew coffee.^[23] This HTTP status is used as an Easter egg in some websites, such as Google.com’s «I’m a teapot» easter egg.^[24]^[25]^[26] Sometimes, this status code is also used as a response to a blocked request, instead of the more appropriate 403 Forbidden.^[27]^[28]
421 Misdirected Request: The request was directed at a server that is not able to produce a response (for example because of connection reuse).
422 Unprocessable Entity: The request was well-formed but was unable to be followed due to semantic errors.^[9]
423 Locked (WebDAV; RFC 4918): The resource that is being accessed is locked.^[9]
424 Failed Dependency (WebDAV; RFC 4918): The request failed because it depended on another request and that request failed (e.g., a PROPPATCH).^[9]
425 Too Early (RFC 8470): Indicates that the server is unwilling to risk processing a request that might be replayed.
426 Upgrade Required: The client should switch to a different protocol such as TLS/1.3, given in the Upgrade header field.
428 Precondition Required (RFC 6585): The origin server requires the request to be conditional. Intended to prevent the ‘lost update’ problem, where a client GETs a resource’s state, modifies it, and PUTs it back to the server, when meanwhile a third party has modified the state on the server, leading to a conflict.^[29]
429 Too Many Requests (RFC 6585): The user has sent too many requests in a given amount of time. Intended for use with rate-limiting schemes.^[29]
431 Request Header Fields Too Large (RFC 6585): The server is unwilling to process the request because either an individual header field, or all the header fields collectively, are too large.^[29]
451 Unavailable For Legal Reasons (RFC 7725): A server operator has received a legal demand to deny access to a resource or to a set of resources that includes the requested resource.^[30] The code 451 was chosen as a reference to the novel Fahrenheit 451 (see the Acknowledgements in the RFC).

5xx server errors

The server failed to fulfil a request.

Response status codes beginning with the digit «5» indicate cases in which the server is aware that it has encountered an error or is otherwise incapable of performing the request. Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and indicate whether it is a temporary or permanent condition. Likewise, user agents should display any included entity to the user. These response codes are applicable to any request method.

500 Internal Server Error: A generic error message, given when an unexpected condition was encountered and no more specific message is suitable.
501 Not Implemented: The server either does not recognize the request method, or it lacks the ability to fulfil the request. Usually this implies future availability (e.g., a new feature of a web-service API).
502 Bad Gateway: The server was acting as a gateway or proxy and received an invalid response from the upstream server.
503 Service Unavailable: The server cannot handle the request (because it is overloaded or down for maintenance). Generally, this is a temporary state.^[31]
504 Gateway Timeout: The server was acting as a gateway or proxy and did not receive a timely response from the upstream server.
505 HTTP Version Not Supported: The server does not support the HTTP version used in the request.
506 Variant Also Negotiates (RFC 2295): Transparent content negotiation for the request results in a circular reference.^[32]
507 Insufficient Storage (WebDAV; RFC 4918): The server is unable to store the representation needed to complete the request.^[9]
508 Loop Detected (WebDAV; RFC 5842): The server detected an infinite loop while processing the request (sent instead of 208 Already Reported).
510 Not Extended (RFC 2774): Further extensions to the request are required for the server to fulfil it.^[33]
511 Network Authentication Required (RFC 6585): The client needs to authenticate to gain network access. Intended for use by intercepting proxies used to control access to the network (e.g., «captive portals» used to require agreement to Terms of Service before granting full Internet access via a Wi-Fi hotspot).^[29]

Unofficial codes

The following codes are not specified by any standard.

218 This is fine (Apache HTTP Server): Used by Apache servers. A catch-all error condition allowing the passage of message bodies through the server when the ProxyErrorOverride setting is enabled. It is displayed in this situation instead of a 4xx or 5xx error message.^[34]
419 Page Expired (Laravel Framework): Used by the Laravel Framework when a CSRF Token is missing or expired.^{[citation needed]}
420 Method Failure (Spring Framework): A deprecated response used by the Spring Framework when a method has failed.^[35]
420 Enhance Your Calm (Twitter): Returned by version 1 of the Twitter Search and Trends API when the client is being rate limited; versions 1.1 and later use the 429 Too Many Requests response code instead.^[36] The phrase «Enhance your calm» comes from the 1993 movie Demolition Man, and its association with this number is likely a reference to cannabis.^{[citation needed]}
430 Request Header Fields Too Large (Shopify): Used by Shopify, instead of the 429 Too Many Requests response code, when too many URLs are requested within a certain time frame.^[37]
450 Blocked by Windows Parental Controls (Microsoft): The Microsoft extension code indicated when Windows Parental Controls are turned on and are blocking access to the requested webpage.^[38]
498 Invalid Token (Esri): Returned by ArcGIS for Server. Code 498 indicates an expired or otherwise invalid token.^[39]
499 Token Required (Esri): Returned by ArcGIS for Server. Code 499 indicates that a token is required but was not submitted.^[39]
509 Bandwidth Limit Exceeded (Apache Web Server/cPanel): The server has exceeded the bandwidth specified by the server administrator; this is often used by shared hosting providers to limit the bandwidth of customers.^[40]
529 Site is overloaded: Used by Qualys in the SSLLabs server testing API to signal that the site can’t process the request.^[41]
530 Site is frozen: Used by the Pantheon Systems web platform to indicate a site that has been frozen due to inactivity.^[42]
598 (Informal convention) Network read timeout error: Used by some HTTP proxies to signal a network read timeout behind the proxy to a client in front of the proxy.^[43]
599 Network Connect Timeout Error: An error used by some HTTP proxies to signal a network connect timeout behind the proxy to a client in front of the proxy.

Internet Information Services

Microsoft’s Internet Information Services (IIS) web server expands the 4xx error space to signal errors with the client’s request.

440 Login Time-out: The client’s session has expired and must log in again.^[44]
449 Retry With: The server cannot honour the request because the user has not provided the required information.^[45]
451 Redirect: Used in Exchange ActiveSync when either a more efficient server is available or the server cannot access the users’ mailbox.^[46] The client is expected to re-run the HTTP AutoDiscover operation to find a more appropriate server.^[47]

IIS sometimes uses additional decimal sub-codes for more specific information,^[48] however these sub-codes only appear in the response payload and in documentation, not in the place of an actual HTTP status code.

nginx

The nginx web server software expands the 4xx error space to signal issues with the client’s request.^[49]^[50]

444 No Response: Used internally^[51] to instruct the server to return no information to the client and close the connection immediately.
494 Request header too large: Client sent too large request or too long header line.
495 SSL Certificate Error: An expansion of the 400 Bad Request response code, used when the client has provided an invalid client certificate.
496 SSL Certificate Required: An expansion of the 400 Bad Request response code, used when a client certificate is required but not provided.
497 HTTP Request Sent to HTTPS Port: An expansion of the 400 Bad Request response code, used when the client has made a HTTP request to a port listening for HTTPS requests.
499 Client Closed Request: Used when the client has closed the request before the server could send a response.

Cloudflare

Cloudflare’s reverse proxy service expands the 5xx series of errors space to signal issues with the origin server.^[52]

520 Web Server Returned an Unknown Error: The origin server returned an empty, unknown, or unexpected response to Cloudflare.^[53]
521 Web Server Is Down: The origin server refused connections from Cloudflare. Security solutions at the origin may be blocking legitimate connections from certain Cloudflare IP addresses.
522 Connection Timed Out: Cloudflare timed out contacting the origin server.
523 Origin Is Unreachable: Cloudflare could not reach the origin server; for example, if the DNS records for the origin server are incorrect or missing.
524 A Timeout Occurred: Cloudflare was able to complete a TCP connection to the origin server, but did not receive a timely HTTP response.
525 SSL Handshake Failed: Cloudflare could not negotiate a SSL/TLS handshake with the origin server.
526 Invalid SSL Certificate: Cloudflare could not validate the SSL certificate on the origin web server. Also used by Cloud Foundry’s gorouter.
527 Railgun Error: Error 527 indicates an interrupted connection between Cloudflare and the origin server’s Railgun server.^[54]
530: Error 530 is returned along with a 1xxx error.^[55]

AWS Elastic Load Balancing

Amazon Web Services’ Elastic Load Balancing adds a few custom return codes to signal issues either with the client request or with the origin server.^[56]

460: Client closed the connection with the load balancer before the idle timeout period elapsed. Typically when client timeout is sooner than the Elastic Load Balancer’s timeout.^[56]
463: The load balancer received an X-Forwarded-For request header with more than 30 IP addresses.^[56]
464: Incompatible protocol versions between Client and Origin server.^[56]
561 Unauthorized: An error around authentication returned by a server registered with a load balancer. You configured a listener rule to authenticate users, but the identity provider (IdP) returned an error code when authenticating the user.^[56]

Caching warning codes (obsoleted)

The following caching related warning codes were specified under RFC 7234. Unlike the other status codes above, these were not sent as the response status in the HTTP protocol, but as part of the «Warning» HTTP header.^[57]^[58]

Since this «Warning» header is often neither sent by servers nor acknowledged by clients, this header and its codes were obsoleted by the HTTP Working Group in 2022 with RFC 9111.^[59]

110 Response is Stale: The response provided by a cache is stale (the content’s age exceeds a maximum age set by a Cache-Control header or heuristically chosen lifetime).
111 Revalidation Failed: The cache was unable to validate the response, due to an inability to reach the origin server.
112 Disconnected Operation: The cache is intentionally disconnected from the rest of the network.
113 Heuristic Expiration: The cache heuristically chose a freshness lifetime greater than 24 hours and the response’s age is greater than 24 hours.
199 Miscellaneous Warning: Arbitrary, non-specific warning. The warning text may be logged or presented to the user.
214 Transformation Applied: Added by a proxy if it applies any transformation to the representation, such as changing the content encoding, media type or the like.
299 Miscellaneous Persistent Warning: Same as 199, but indicating a persistent warning.

Explanatory notes

^ Emphasised words and phrases such as must and should represent interpretation guidelines as given by RFC 2119

References

^ ^a ^b ^c «Hypertext Transfer Protocol (HTTP) Status Code Registry». Iana.org. Archived from the original on December 11, 2011. Retrieved January 8, 2015.
^ Fielding, Roy T. «RFC 9110: HTTP Semantics and Content, Section 10.1.1 «Expect»«.
^ Goland, Yaronn; Whitehead, Jim; Faizi, Asad; Carter, Steve R.; Jensen, Del (February 1999). HTTP Extensions for Distributed Authoring – WEBDAV. IETF. doi:10.17487/RFC2518. RFC 2518. Retrieved October 24, 2009.
^ «102 Processing — HTTP MDN». 102 status code is deprecated
^ Oku, Kazuho (December 2017). An HTTP Status Code for Indicating Hints. IETF. doi:10.17487/RFC8297. RFC 8297. Retrieved December 20, 2017.
^ Stewart, Mark; djna. «Create request with POST, which response codes 200 or 201 and content». Stack Overflow. Archived from the original on October 11, 2016. Retrieved October 16, 2015.
^ «RFC 9110: HTTP Semantics and Content, Section 15.3.4».
^ «RFC 9110: HTTP Semantics and Content, Section 7.7».
^ ^a ^b ^c ^d ^e Dusseault, Lisa, ed. (June 2007). HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV). IETF. doi:10.17487/RFC4918. RFC 4918. Retrieved October 24, 2009.
^ Delta encoding in HTTP. IETF. January 2002. doi:10.17487/RFC3229. RFC 3229. Retrieved February 25, 2011.
^ ^a ^b «RFC 9110: HTTP Semantics and Content, Section 15.4 «Redirection 3xx»«.
^ Berners-Lee, Tim; Fielding, Roy T.; Nielsen, Henrik Frystyk (May 1996). Hypertext Transfer Protocol – HTTP/1.0. IETF. doi:10.17487/RFC1945. RFC 1945. Retrieved October 24, 2009.
^ «The GNU Taler tutorial for PHP Web shop developers 0.4.0». docs.taler.net. Archived from the original on November 8, 2017. Retrieved October 29, 2017.
^ «Google API Standard Error Responses». 2016. Archived from the original on May 25, 2017. Retrieved June 21, 2017.
^ «Sipgate API Documentation». Archived from the original on July 10, 2018. Retrieved July 10, 2018.
^ «Shopify Documentation». Archived from the original on July 25, 2018. Retrieved July 25, 2018.
^ «Stripe API Reference – Errors». stripe.com. Retrieved October 28, 2019.
^ «RFC2616 on status 413». Tools.ietf.org. Archived from the original on March 7, 2011. Retrieved November 11, 2015.
^ «RFC2616 on status 414». Tools.ietf.org. Archived from the original on March 7, 2011. Retrieved November 11, 2015.
^ «RFC2616 on status 416». Tools.ietf.org. Archived from the original on March 7, 2011. Retrieved November 11, 2015.
^ TheDeadLike. «HTTP/1.1 Status Codes 400 and 417, cannot choose which». serverFault. Archived from the original on October 10, 2015. Retrieved October 16, 2015.
^ Larry Masinter (April 1, 1998). Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0). doi:10.17487/RFC2324. RFC 2324. Any attempt to brew coffee with a teapot should result in the error code «418 I’m a teapot». The resulting entity body MAY be short and stout.
^ I’m a teapot
^ Barry Schwartz (August 26, 2014). «New Google Easter Egg For SEO Geeks: Server Status 418, I’m A Teapot». Search Engine Land. Archived from the original on November 15, 2015. Retrieved November 4, 2015.
^ «Google’s Teapot». Retrieved October 23, 2017.^{[dead link]}
^ «Enable extra web security on a website». DreamHost. Retrieved December 18, 2022.
^ «I Went to a Russian Website and All I Got Was This Lousy Teapot». PCMag. Retrieved December 18, 2022.
^ ^a ^b ^c ^d Nottingham, M.; Fielding, R. (April 2012). «RFC 6585 – Additional HTTP Status Codes». Request for Comments. Internet Engineering Task Force. Archived from the original on May 4, 2012. Retrieved May 1, 2012.
^ Bray, T. (February 2016). «An HTTP Status Code to Report Legal Obstacles». ietf.org. Archived from the original on March 4, 2016. Retrieved March 7, 2015.
^ alex. «What is the correct HTTP status code to send when a site is down for maintenance?». Stack Overflow. Archived from the original on October 11, 2016. Retrieved October 16, 2015.
^ Holtman, Koen; Mutz, Andrew H. (March 1998). Transparent Content Negotiation in HTTP. IETF. doi:10.17487/RFC2295. RFC 2295. Retrieved October 24, 2009.
^ Nielsen, Henrik Frystyk; Leach, Paul; Lawrence, Scott (February 2000). An HTTP Extension Framework. IETF. doi:10.17487/RFC2774. RFC 2774. Retrieved October 24, 2009.
^ «218 This is fine — HTTP status code explained». HTTP.dev. Retrieved July 25, 2023.{{cite web}}: CS1 maint: url-status (link)
^ «Enum HttpStatus». Spring Framework. org.springframework.http. Archived from the original on October 25, 2015. Retrieved October 16, 2015.
^ «Twitter Error Codes & Responses». Twitter. 2014. Archived from the original on September 27, 2017. Retrieved January 20, 2014.
^ «HTTP Status Codes and SEO: what you need to know». ContentKing. Retrieved August 9, 2019.
^ «Screenshot of error page». Archived from the original (bmp) on May 11, 2013. Retrieved October 11, 2009.
^ ^a ^b «Using token-based authentication». ArcGIS Server SOAP SDK. Archived from the original on September 26, 2014. Retrieved September 8, 2014.
^ «HTTP Error Codes and Quick Fixes». Docs.cpanel.net. Archived from the original on November 23, 2015. Retrieved October 15, 2015.
^ «SSL Labs API v3 Documentation». github.com.
^ «Platform Considerations | Pantheon Docs». pantheon.io. Archived from the original on January 6, 2017. Retrieved January 5, 2017.
^ «HTTP status codes — ascii-code.com». www.ascii-code.com. Archived from the original on January 7, 2017. Retrieved December 23, 2016.
^
«Error message when you try to log on to Exchange 2007 by using Outlook Web Access: «440 Login Time-out»«. Microsoft. 2010. Retrieved November 13, 2013.
^ «2.2.6 449 Retry With Status Code». Microsoft. 2009. Archived from the original on October 5, 2009. Retrieved October 26, 2009.
^ «MS-ASCMD, Section 3.1.5.2.2». Msdn.microsoft.com. Archived from the original on March 26, 2015. Retrieved January 8, 2015.
^ «Ms-oxdisco». Msdn.microsoft.com. Archived from the original on July 31, 2014. Retrieved January 8, 2015.
^ «The HTTP status codes in IIS 7.0». Microsoft. July 14, 2009. Archived from the original on April 9, 2009. Retrieved April 1, 2009.
^ «ngx_http_request.h». nginx 1.9.5 source code. nginx inc. Archived from the original on September 19, 2017. Retrieved January 9, 2016.
^ «ngx_http_special_response.c». nginx 1.9.5 source code. nginx inc. Archived from the original on May 8, 2018. Retrieved January 9, 2016.
^ «return» directive Archived March 1, 2018, at the Wayback Machine (http_rewrite module) documentation.
^ «Troubleshooting: Error Pages». Cloudflare. Archived from the original on March 4, 2016. Retrieved January 9, 2016.
^ «Error 520: web server returns an unknown error». Cloudflare.
^ «527 Error: Railgun Listener to origin error». Cloudflare. Archived from the original on October 13, 2016. Retrieved October 12, 2016.
^ «Error 530». Cloudflare. Retrieved November 1, 2019.
^ ^a ^b ^c ^d ^e «Troubleshoot Your Application Load Balancers – Elastic Load Balancing». docs.aws.amazon.com. Retrieved May 17, 2023.
^ «Hypertext Transfer Protocol (HTTP/1.1): Caching». datatracker.ietf.org. Retrieved September 25, 2021.
^ «Warning — HTTP | MDN». developer.mozilla.org. Retrieved August 15, 2021. Some text was copied from this source, which is available under a Creative Commons Attribution-ShareAlike 2.5 Generic (CC BY-SA 2.5) license.
^ «RFC 9111: HTTP Caching, Section 5.5 «Warning»«. June 2022.

External links

«RFC 9110: HTTP Semantics and Content, Section 15 «Status Codes»«.
Hypertext Transfer Protocol (HTTP) Status Code Registry at the Internet Assigned Numbers Authority
HTTP status codes at http-statuscode.com
MDN status code reference at mozilla.org

Источник

I have a mobile device communicating via HTTPS to a RESTful API on my servers. One of the operations is a data sync to push modifications made while offline to the server and pull down updates made in parallel on the server.

I’ve encountered an edge case where that sync operation can fail silently in the existing client. I’ve upgraded the «sync protocol» on the client to handle the condition properly. Ideally I’d like to have all older clients receive a message when they try to sync telling them to upgrade.

The communication is just between my server and my mobile client so I realize I can return any number of HTTP codes and signal the client to display a message in the future advising the user to upgrade and to immediately stop the sync process.

Would it be seen as a bastardization of the intent of the HTTP 426 Upgrade Required return code to use it to signal this. Every reference (IETF RFC 2817, Wikipedia) I can find speaks to using it to signal a client to upgrade to TLS. Is it meant to be limited to well defined/security protocols like SSL and TLS or is it a generic upgrade flag at the HTTP layer which has only been used for SSL and TLS traditionally?

If it isn’t intended for this use case would a HTTP 303 See Other be considered more appropriate or is there another code I’m missing?

Bruno

120k31 gold badges270 silver badges376 bronze badges

asked Jul 26, 2013 at 5:00

Quoting one of my previous answers:

HTTP Upgrade is used to indicate a preference or requirement to
switch to a different version of HTTP or to another protocol, if
possible:
The Upgrade general-header allows the client to specify what 
additional communication protocols it supports and would like to use 
if the server finds it appropriate to switch protocols. The server 
MUST use the Upgrade header field within a 101 (Switching Protocols) 
response to indicate which protocol(s) are being switched.

      Upgrade        = "Upgrade" ":" 1#product

  For example,

     Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11

The Upgrade header field is intended to provide a simple mechanism 
for transition from HTTP/1.1 to some other, incompatible protocol.
According to the IANA register, there are only 3 registered
mentions of it (including one in the HTTP specification itself).

The other two are for:

Upgrading to TLS Within HTTP/1.1 (almost never used, not to
be confused with HTTP over TLS, which defines HTTPS as widely
used). This upgrade allows for a similar mechanism to STARTTLS in
other protocols (e.g. LDAP, SMTP, …) so as to be able to switch
to TLS on the same port as the plain connection, after exchanging some
of the application protocol messages, as opposed to having the entire
HTTP exchange on top of SSL/TLS without it needing to know it’s on top
of TLS (the way HTTPS works).

Upgrading to WebSockets (still a draft).

(The IANA register hasn’t changed since then.)

The 426 response code as defined in RFC 2817 clearly has to do with an upgrade in the «HTTP Upgrade» sense defined in RFC 2816. This is a change of the current protocol at the layer currently used (i.e. HTTP itself). (It’s not even about upgrading from http:// to https:// at all.)

The messages exchanged on top of HTTP (if part of a protocol at all) are not part of this. They’re just hypermedia entities as far as HTTP is concerned.

I don’t think 426 would be suitable if you change the meaning of your hypermedia. A plain 400 would probably be a better choice. Note that responses with error status codes (4xx, 5xx) do not prevent you from associating an entity in the response: this is where a message telling the client to upgrade your protocol (at that level) should be.

answered Jul 26, 2013 at 10:49

BrunoBruno

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I agree with Bruno that 426 is not the best choice. 400 is better, but I think 403 is better still.

10.4.4 403 Forbidden

The server understood the request, but is refusing to fulfill it. Authorization will not help and the request SHOULD NOT be repeated. If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled, it SHOULD describe the reason for the refusal in the entity. If the server does not wish to make this information available to the client, the status code 404 (Not Found) can be used instead.

There is precedent for this on the Twitter API.

Since Feb 26, 2014, api.twitter.com is returning 403 status code for all non-SSL incoming traffic. Your client code should be able to handle this error.

answered Apr 17, 2014 at 1:05

Chris H.Chris H.

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Источник

426 CODE REFERENCES

426 status code example

Request

Response

What causes a 426 status code?

How to troubleshoot a 426 status code

Additional resources

Usage

Example

Code references

Takeaway

See also

What Is 426 Http Status Code?

Cause Of 426 Http Status Code Error

Server Side Or Client Side Issue?

How To Fix 426 Http Status Code Error

Example

Similar Http Status Codes To 426

All HTTP status codes by categories

1xx informational response

2xx success

3xx redirection

4xx client errors

5xx server errors

Unofficial codes

Internet Information Services

nginx

Cloudflare

AWS Elastic Load Balancing

Caching warning codes (obsoleted)

See also

Explanatory notes

References

External links

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