You have a website: http://www.mysite.com

You want to serve up mobile-optimized pages for mobile devices. I've seen a lot of companies redirect mobile devices to this type of subdomain:


Also, I've seen a lot of companies use subdomains for localization:

http://it.mysite.com (Italian)
http://de.mysite.com (Deutsch)
http://es.mysite.com (Espanol)

A obvious site that does this is http://www.wikipedia.org

Anyways, my question: Is using subdomains like this bad for SEO because of the potential for duplicate content between the sites or other SEO reasons? I've seen a LOT of companies do this, but I've also read that it's not a good practice.

2 Answers 2


Google recently explained how to handle multilingual situations like this. Their example shows the usage of subdomains but you can use domains as well:

<link rel="alternate" hreflang="en" href="http://www.company.com/" />
<link rel="alternate" hreflang="es-ES" href="http://company.es/" />
<link rel="alternate" hreflang="es-MX" href="http://companymx.es/" />

As far as mobile websites go, they covered that here.

A very common question we see is: Does it matter if the different types of content are served from the same URL or from different URLs? For example, some websites have www.example.com as the URL desktop browsers are meant to access and have m.example.com or wap.example.com for the different mobile devices. Other websites serve all types of content from just one URL structure like www.example.com.

For Googlebot and Googlebot-Mobile, it does not matter what the URL structure is as long as it returns exactly what a user sees too. For example, if you redirect mobile users from www.example.com to m.example.com, that will be recognized by Googlebot-Mobile and both websites will be crawled and added to the correct index. In this case, use a 301 redirect for both users and Googlebot-Mobile.

If you serve all types of content from www.example.com, i.e. serving desktop-optimized content or mobile-optimized content from the same URL depending on the User-agent, this will also lead to correct crawling by Googlebot and Googlebot-Mobile. This is not considered cloaking by Google.

It is worth repeating that regardless of URL structure, you must correctly detect the User-agent as given by your users and Googlebot-Mobile, and serve both the same content. Don’t forget to keep the default content, the desktop-optimized content, for when an unknown User-agent requests it.

  • 1
    How about the duplicate content concerns? Mobile sites are going to have extremely similar (if not exactly the same) content that it's full/desktop site is going to have. Does Google take this into account? Are there any articles out there where Google specifically discusses this topic? Commented Jan 26, 2012 at 3:06

Its a good idea. Please remember, when it's good for your users, its good for SEO.

SEO is dynamic and evolving all the time, do not think it's hard cold rule to follow.

  • This doesn't answer the question
    – John Conde
    Commented Jan 26, 2012 at 17:46

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