Use Proxy

3xx Redirection

ELI5

This is an old HTTP idea that said, 'Use this proxy instead,' but modern systems should not rely on it.

Do not emit 305 in modern systems; keep it as historical reference material only.

•Avoid 305 for real application behavior because it is deprecated and unsafe as a proxy-configuration signal
•Use explicit proxy setup or ordinary redirect codes instead of trying to steer clients through a proxy this way
•When reading historical HTTP documentation or troubleshooting legacy traffic captures
•When teaching why modern HTTP avoids server-directed proxy configuration

•If you maintain a legacy component that still knows about 305, plan to remove or replace that behavior
•Do not introduce new 305 responses in APIs, gateways, or web applications

•No modern product flow should depend on a 305 response body; the historical proxy target was carried in Location

•Do not use 305 as a shortcut for network routing or access control
•Do not trust clients to safely follow proxy instructions delivered in-band
•Modern APIs, browsers, or application redirects
•Proxy authentication flows; use explicit proxy configuration and 407 where appropriate
•Temporary or permanent resource moves; use the normal redirect codes instead

Request:GET https://api.example.test/resource

Response:

305 Use Proxy

# Headers
Location: http://proxy.example.net:8080

This reflects the historical meaning, but modern clients generally should not obey such instructions automatically.

This number exists in the HTTP list, but it does not mean anything you should use in a real app today.

Go to this other address for now, and send the exact same kind of request there.

You need to authenticate with the proxy server first before it will forward your request to the destination.