Fiddler Classic x-overrideHost Preserves the HTTP Host Header

Use x-overrideHost for a development destination mapping while keeping the HTTP virtual-host name intact.

For a development HTTP request captured by Fiddler Classic, x-overrideHost changes the connection destination while preserving the request’s Host header. Put the rule in OnBeforeRequest:

if (oSession.HostnameIs("preview.example.net")) {
    oSession.bypassGateway = true;
    oSession["x-overrideHost"] = "192.0.2.20";
}

Replace the documentation address with the development server. The browser can keep requesting preview.example.net, and the server still receives that virtual-host name. This is useful when replacing the URL hostname with an IP would select the wrong application.

bypassGateway deliberately sends this connection without Fiddler’s configured upstream proxy. Keep it only when that direct development route is intended and reachable. Otherwise the parent proxy can remain responsible for a different destination decision.

The rule affects sessions passing through Fiddler. It does not edit the operating system’s hosts file or change another program’s uncaptured connection.

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