426 Upgrade Required
Not until you upgrade that old shit.
What it properly means
The server refuses the request on the current protocol but might accept it after the client upgrades. The Upgrade header names the required protocols.
- Class
- 4xx Client error: you fucked up
- Defined in
- RFC 9110, section 15.5.22
Get one yourself
This endpoint really answers with 426. Point your client at it and see what it does.
curl -i https://httpcodes.dev/api/426