(Unused / Reserved)
Production Risk
Low — you will never encounter this in production unless dealing with ancient or broken infrastructure.
306 is permanently reserved and unused. It appeared in an early draft of RFC 2068 without any assigned semantics and was explicitly retired in RFC 7231. The label 'Switch Proxy' that appears on Wikipedia and many reference sites has no RFC basis — it was never the official name. No conforming server should ever return 306 and no client should act on it.
- 1306 was reserved in an early draft of RFC 2068 but never received defined semantics.
- 2RFC 7231 §6.4.6 explicitly states the code is no longer used.
- 3If encountered, it indicates a very old or non-compliant server; treat it as an error.
Historical — not generated by any modern server.
GET / HTTP/1.1 Host: example.com
expected output
HTTP/1.1 306 (Unused)
Fix
Do not use 307 Temporary Redirect instead
WHEN You are building a server and want to redirect clients to a proxy.
HTTP/1.1 307 Temporary Redirect Location: http://proxy.example.com/
Why this works
307 is the correct modern replacement for the proxy-redirect intent.
✕ Do not emit 306 from any server
It is reserved and undefined in the current HTTP spec; clients will not know how to handle it.
Was defined in an early draft of RFC 2068 but removed before the final specification. The code is permanently reserved.
RFC 9110 §15.4.7 (reserved)
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/306 ↗Content generated with AI assistance and reviewed for accuracy. Found an error? hello@errcodes.dev