To copy the HTML document of the WebBrowser control in HTML format, you need to use the IHTMLDocument2 object of the MSHTML class.

For this, you need to add a reference to Microsoft.mshtml assembly which can be found in C:Program FilesMicrosoft.NETPrimary Interop Assemblies folder. Then write the following code in a button click event (btnCopyTextAsHTML in my example).

private void btnCopyTextAsHTML _Click(object sender, EventArgs e) {    HtmlDocument document = myWebBrowser.Document;    if (document != null)    {      document.ExecCommand("SelectAll", false, null);      IHTMLDocument2 htmlDocument = document.DomDocument as IHTMLDocument2;      (htmlDocument.selection.createRange() as IHTMLTxtRange).execCommand("Copy", false, null);   } }