Alberto Pastore:

I'm trying to force a specific Referrer Header when loading a URL in CefSharp OffScreen. I've followed examples and suggestions which indicate to do that inside IRequestHandler.OnBeforeResourceLoad. Nothing happens, the referrer header is not sent in the request.

Here is a snippet from my tests:

public class CefWorker: IRequestHandler
{
    ChromiumWebBrowser Browser;
    string InitialUrl;

    // ... constructor and other methods here ...

    public void Run()
    {
        InitialUrl = "https://www.msoft.it/about/chi-siamo/";

        CefSettings Settings = new CefSettings()
        {
            WindowlessRenderingEnabled = true,
            LogSeverity = LogSeverity.Disable
        };
        Settings.SetOffScreenRenderingBestPerformanceArgs();
        Cef.Initialize(Settings, performDependencyCheck: Program.Settings.CheckCefDependencies, browserProcessHandler: null);
        Browser = new ChromiumWebBrowser()
        {
            RequestHandler = this
        };
        Browser.BrowserInitialized += (o, e) => { Browser.Load(InitialURL); };        
    }

    public CefReturnValue OnBeforeResourceLoad(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IRequestCallback callback)
    {
        if (request.Url == InitialUrl) {
            request.SetReferrer("https://www.msoft.it/", ReferrerPolicy.Always);

            // tried also this but it won't work
            // request.Headers["Referer"] = "https://www.msoft.it/";

            // this header is present in the request
            request.Headers["X-MyCustomHeader"] = "My-Custom-Value";
        }

        return CefReturnValue.Continue;
    }
}

When I dump the headers on server side, I can find

X-MyCustomHeader: My-Custom-Value

but there is no trace of Referer:

I'm testing this using CefSharp 63.0.0-pre02. What am I doing wrong?