What's better for SEO: using a sub-domain or directory of a domain name?

Let’s say your main American site is xxx.com

What would be better for the Australian site from an SEO perspective please?

australia.xxx.com or xxx.com/australia


In this example I would say the sub domain. The main question here would be is if this a translation of the site, or is it a completely different website? Seeing how it’s Australian/American I am assuming it’s not a translation but rather a different site that serves a different function.

Search engines see sub domains as different sites, but like a child of the main site. Sub folders are generally considered a sub part of the main site, rather than a separate site. I would recommend the sub domain route for a couple different reasons:

(1) You could use an Australian host to host the sub domain and keep it more local.
(2) If you’re submitting to a lot of local Australian directories or catalogs, it won’t clash with your root level link building campaign(s) other wise cause confusion.

Again, the flip side is if you’re just making a slight variation - for example a store that charges in AUD instead of USD, or different model numbers but the same product, then your best bet would be to do it in a sub folder rather than a sub domain, autoredirect based on Geo location and perhaps block the folder via robots.txt so your Australian content isn’t considered duplicate content.

Hope that helps.

I think here you’ll get your answer from matt cutts, …mattcutts.com/blog/subdomains-and-subdirectories/

[FONT=Verdana]I would generally avoid subdomains altogether. The principle reason being that the majority of web surfers struggle to type in a normal domain name and can’t cope with anything that doesn’t begin with [noparse]www.[/noparse]. It’s annoying enough when I’m giving someone a URL to type in and they ask “Do I need to type [noparse]www dot[/noparse]?” even when it doesn’t matter, but if you’ve got a subdomain then it does matter and anyone typing [noparse]www.australia.xxx.com[/noparse] is going to get a honking big error message.

A few other factors that mitigate against using subdomains are:

[list][]Re-use of resources. If you’ve gone for subfolders then you can easily reference images, stylesheets and scripts with eg href="/global/style/theme.css", whereas if you’ve gone for subdomains then you have to include the full domain name in the URL for any shared resource – while it isn’t a huge deal, it will have an impact on your site’s performance.
]Lots of places will automatically convert anything they recognise as a URL into a clickable link – word processors, email clients, text messages, forums and social media websites etc. But that only works if the URL starts with [noparse]http:// or www.[/noparse]. If you have a subdomain then to make those links clickable then you need to type in the (rather ugly) [noparse]http://[/noparse] at the start of every one, whereas with subfolders you can go for the simpler [noparse]www.[/noparse] instead.[/list]

OK, I haven’t mentioned SEO much (except that the more times your URL is automatically linkified around the web, the more links to your site there are), but that’s because I really don’t think it matters. Google wants to give surfers the best sites it can. That isn’t going to be affected by whether you’ve got example.com/australia, example.com.au or au.example.com – it makes no difference to the quality of reputation of the site, so Google is unlikely to pay any attention to it.[/FONT]