Sadly, you won't be able to do that with FMX's TWebBrowser. It simply doesn't have the necessary functionality for that (only VCL's TWebBrowser does). If you really want to use FMX's TWebBrowser, then I suggest using TIdHTTP or other HTTP client for the actual HTTP communications, that way you can automate it however you want, and just use TWebBrowser to display the HTML (or whatever) you retrieve, such as via its LoadFromStrings() method. And then use TWebBrowser events to block the browser from making HTTP requests, redirecting them to your HTTP client of choice. The experience won't be as seemless as a standard browser, but it will give you more control.