HTTP registry: http_upgrade_failed

The process of negotiating an upgrade of the HTTP version between the intermediary and the next hop failed.

Proxy and gateway values describe processing across trust boundaries where fields, authority, and framing may be transformed. http_upgrade_failed is registered in HTTP Proxy Error Types. Defining reference: rfc9209.

httpregistryhttp-proxy-statushttp-proxy-error-types

Identifier (http)

http_upgrade_failed

The process of negotiating an upgrade of the HTTP version between the intermediary and the next hop failed.

Strip hop-by-hop data, normalize framing, trust forwarded metadata only from configured proxies, and avoid exposing topology or credentials.

This registry value is currently marked active by IANA. Follow the defining specification before sending, accepting, or proxying it.

IANA registry: http-proxy-status/http-proxy-error-types

Registry reference: rfc9209

Sources

HTTP Proxy Error Types
rfc9209