426 Upgrade Required

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/3.0 
Connection: Upgrade 
Content-Length: 53 
Content-Type: text/plain 

This service requires use of the HTTP/3.0 protocol

Specifications

See also

• Upgrade
• 101 Switching Protocol