Choosing an Extension You could be wondering why I choose â€œ.com.auâ€ for some of my domain examples. I use that to set examples for businesses in Australia. I used â€œcom.auâ€, which is a local extension, to target a specific geographical area which is Australia. For websites targeting a specific geographical location, it is best to use a local extension. But if you are targeting a global audience, it is imperative to use â€œ.comâ€.