I would leave off this: agent_alias( 'Windows Mozilla' ) and use the default. I am not sure that this string without version info would be recognized as a known browser. When I am pretending to be something too stupid to know Java, I use: $ua->agent("Mozilla/4.76 [en] (Windows NT 5.0; U)"); You can definitely get different results depending upon what kind of browser you claim to be (this is not always the case, but it does happen).