407 Proxy Authentication Required

407 Proxy Authentication Required is similar to 401 Unauthorized, but authentication must be performed through a proxy intermediary. The proxy server must include a Proxy-Authenticate header in the response, indicating the authentication scheme.

This is common in corporate environments where all traffic flows through an authenticated proxy.

• Corporate proxy requiring authentication credentials
• Misconfigured proxy settings in the browser or client
• VPN or network gateway with mandatory auth
• Expired proxy credentials

• Configure proxy credentials in browser or HTTP client settings
• Check Proxy-Authenticate header for the required auth scheme
• Contact network admin if proxy credentials have expired
• Use Proxy-Authorization header in subsequent requests