426 Upgrade Required

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This response error indicates the server refused the request due to the current protocol being used.

Usually, this response means the server will accept the request if the client upgrades to an alternate protocol. An example would be upgrading to a secure protocol such as TLS or SSL.

The server should send this error response with an Upgrade header indicating the required protocols.

If this error is unexpected verify the requirements of the request and attempt again with the required protocols.

If the issue persists with the required protocols then contact server support for help.

The HTTP 426 Upgrade Required client error response code indicates that 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 sends an Upgrade header with this response to indicate the required protocol(s).

Status

426 Upgrade Required

Examples

HTTP/1.1 426 Upgrade Required
Upgrade: HTTP/2.0
Connection: Upgrade
Content-Length: 53
Content-Type: text/plain

This service requires use of the HTTP/2.0 protocol

Specifications

Specification	Title
RFC 7231, section 6.5.15: 426 Upgrade Required	Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content