public class CustomResourceRequestHandler : ResourceRequestHandler { protected override CefReturnValue OnBeforeResourceLoad(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, IRequest request, IRequestCallback callback) { var headers = request.Headers; headers["User-Agent"] = "My User Agent"; request.Headers = headers; return CefReturnValue.Continue; } } public class CustomRequestHandler : RequestHandler { protected override IResourceRequestHandler GetResourceRequestHandler(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, IRequest request, bool isNavigation, bool isDownload, string requestInitiator, ref bool disableDefaultHandling) { return new CustomResourceRequestHandler(); } } ChromiumWebBrowser myBrowser = new ChromiumWebBrowser("whatever.com") { RequestHandler = new CustomRequestHandler(); };