Transparent proxy

A transparent proxy adds headers to the request, such as X-Forwarded-For with the client's real address or Via with a proxy mark. The site sees both the proxy and you.

Such proxies are installed by ISPs, schools and offices for caching or filtering. Often the user does not even configure them: traffic is intercepted in the network.

For work where the site has to see a different address, a transparent proxy is not suitable. There you need an anonymous or an elite proxy.

You can check which headers reach websites with the proxy checker and the My IP page.

How a transparent proxy intercepts traffic

The browser has no proxy settings at all. The router or network gateway redirects outgoing connections on port 80 to the proxy server, and it answers on behalf of the site. The user notices nothing, except sometimes a block page or an old cached copy of a page.

With HTTPS such a proxy sees much less. Without decryption it learns only the site name from SNI and the amount of data, but not the pages or the headers. Full inspection of HTTPS is possible only when the device trusts the network's root certificate, as is often the case on corporate laptops.

How to check your own network

• Open the My IP page without a proxy and compare the address with the one shown in your router or ISP account.
• Compare how a plain HTTP page and an HTTPS page behave: transparent proxies usually work only with port 80.
• If you have your own server, look in its logs for Via or X-Forwarded-For headers in your requests.
• On a work computer, check who issued the certificate of an HTTPS site: your company's name instead of a public certificate authority means traffic inspection.

When you work through Prokso from such a network

A transparent proxy that intercepts port 80 usually does not touch connections to Prokso ports such as 823, 824 or 10000-20000. For HTTPS sites the request goes inside a CONNECT tunnel, so the content stays encrypted between your program and the site. If the network lets out only ports 80 and 443, connections to Prokso ports may not get through at all, and that is a question for the network administrator.