HTTP 426 Upgrade Required indicates the server refuses to perform the request using the current protocol but would be willing to do so if the client upgrades to a different protocol. The server MUST include an Upgrade header indicating the required protocol(s). This is used to enforce HTTPS (Upgrade: TLS/1.2), HTTP/2 (Upgrade: h2c), or WebSocket connections on endpoints that require them.
Response includes the status code, standard headers (including Content-Type), and a small diagnostic JSON body describing the request and returned status.
Simulator URL (copy in the app after load — not a normal link):
https://httpstatus.com/api/status/426
Example request:
curl -i "https://httpstatus.com/api/status/426"