Proxy HTTP headers

HTTP request fields that can indicate traffic passed through an intermediary proxy.

What proxy headers reveal

A proxy may add headers such as Forwarded, Via, or X-Forwarded-For when it sends a request to a website on behalf of a client.

The presence of a header can be a useful signal, but it does not prove that a privacy proxy or VPN is active. Trusted reverse proxies and corporate gateways use the same mechanisms, and headers can be removed or forged.