To test - Go to appearance/theme selector Specify a default theme This will display on any device Go to appearance/theme selector Specify a different mobile or a tablet theme or legacy (IE6) (depends what you have easily available to test). This should appear on the type of device. The default theme will remain on a standard desktop. Go to Advanced features and untick enable device detection. The default theme should be used on any device. Go to theme selector and the list of devices will not show - you can only specify a default theme. Go Advanced features, tick enable device detection. In Device Detection regular expression add /fox/ and under returns value add firefox. In the theme selector, select a different theme to use for firefox (similar should work for ie, chrome, etc)