426 Upgrade Required
The 426 HTTP response status code is used by the server to inform the client that it cannot process the request using the current protocol version.
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Introduction
In Action
Sample
Conclusion
Introduction
The HTTP response status code 426 Update Required is used by the server to inform the client that it cannot process the request using the current protocol version.
The server suggests that the client upgrades to a different protocol to proceed, but there is no guarantee that the server will accept the request even after the upgrade. However, upgrading the protocol might increase the chances of successful processing by the server.
In Action
When you receive the 426 Upgrade Required status code, the server includes an Upgrade response header field, specifying the protocol(s) that need to be used for successful processing.
This status is related to the 101 Switching Protocols message, which occurs when the client requests the server to upgrade the connection to a different protocol. Keep in mind that search engines like Google won’t index URLs with a 426 response status, ensuring they won’t appear in search results.
Sample
In this example, the client initially requests a resource, but the server indicates that it requires an upgrade to support HTTP/2 or HTTP/3 protocols.
The client complies and upgrades the connection to HTTP/2, and then the server responds with a 101 Switching Protocols message. Now, the request is successfully processed using the upgraded protocol.
Initial request
GET /tech-news HTTP/1.1
Host: www.example.com
Initial response, won’t 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.com
Connection: upgrade
Upgrade: HTTP/2
Informational response
HTTP/1.1 101 Switching Protocols
Upgrade: HTTP/2
Connection: upgrade
Conclusion
The 426 Upgrade Required status code is used by the server to indicate that the client’s current protocol version is not supported, and an upgrade to a different protocol is required to proceed.
This response may require the client to switch to a newer protocol version to continue communicating with the server effectively.
