407

Proxy Authentication Required

4xx Client Error

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ELI5

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

Server perspective

Use 407 when a proxy requires authentication before it will forward the request.

When to use

  • •Return 407 from the proxy, not the origin server
  • •Use it when the client must authenticate to the intermediary itself
  • •Corporate proxy requires authentication
  • •Authenticated proxy servers
  • •Network security proxy authentication
  • •Content filtering proxy login

How to respond

  • •Include Proxy-Authenticate so the client knows which proxy auth scheme to use
  • •Expect the retried request to carry Proxy-Authorization

Headers to consider

  • •Proxy-Authenticate

Response body

  • •Optionally include a short proxy-authentication error; avoid leaking credential details.

Server-side pitfalls

  • •Do not confuse 407 proxy auth with 401 origin-server auth
  • •Do not rely on origin-application error handling to explain proxy failures clearly
  • •Origin server authentication (use 401 Unauthorized)
  • •General authorization issues (use 403 Forbidden)
  • •Network-level auth (use 511 Network Authentication Required)

Examples

Corporate proxy authentication

Request:GET https://api.example.test/external-resource # Headers Host: example.com
Response:407 Proxy Authentication Required # Headers Proxy-Authenticate: Basic realm="corporate-proxy"

Must provide credentials to corporate proxy before accessing external sites

References

Related Status Codes

401

Unauthorized

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