I have created a subdomain for a town in San Diego that's ranking very well for it's keywords: http://carmelvalleymortgage.loanrebateinc.com/

I want to replicate this subdomain's content for another town in San Diego: http://sandiego.mortgage.loanrebateinc.com/

I will edit the text, tags, image files specific to each town, otherwise the verbiage will be identical.


  1. Will Google penalize the main site?
  2. Will Google penalize the subdomains and list the content as spam?
  3. If yes to either 1 or 2, what strategies can I implement to prevent this?

I'm using WordPress.

3 Answers 3


Web crawlers (Googlebot, Bingbot...) compare HTML text found on differents websites (a subdomain is considered as an other website compared to your main site). If they find duplicate content for text, search engines can penalize the site with the smallest SEO authority (and in general if the page with duplicate content is found after the page with original content).

However, even if you speak about the same city, if the content is different, there is no problem for SEO. Think that multiple websites can speak about the same city and search engines can penalize all these websites.


  1. No
  2. No
  3. -

Otherwise, duplicate content is independant of CMS (WordPress, Drupal...) you can use.

  • I plan on creating 35 subdomains for 35 towns within the city, do you this number is too high?
    – John Pham
    Oct 24, 2013 at 20:56
  • It depends. If you use different CMS with strictly different content on each site, it can be work (avoid to link sites together). However, to produce all this original content about this city, you need many months, years of work.
    – Zistoloen
    Oct 24, 2013 at 21:23
  • Actually, WP clone plugin makes site replication very easy and fast, in fact I can create 35 sites at the pace of 1/week, so time is not an issue. The fear I have is Google penalizing the main site (loanrebateinc.com) and the all the subdomians for duplicate content. I have achieved #1 ranking for the main site and the first subdomiain site (carmelvalleymortgage.loanrebateinc.com), this took a lot of work and don't want to see it go down the drain.
    – John Pham
    Oct 25, 2013 at 17:03
  • Google considers subdomains as different websites than the main site. For me, there is no risk for the main site. At worst, Google will penalize subdomains but it's unlikely if your subdomains have different and original content. However, if you have doubts, don't do it, you already have a good ranking for the main site.
    – Zistoloen
    Oct 25, 2013 at 19:59
  • Grazie, I'll proceed slowly and see how Google responds. Either way, I'll update this post with my results.
    – John Pham
    Oct 25, 2013 at 21:57

Duplicate content can be created in many ways. www.domain.com, www.domain.com/index.html, domain.com, domain.com/index.html?id=shoppingcartuserid This is before considering subdomains. Are these pages quote unquote spam? no but they are also not ideal.

It is a waste of space for the search engine to maintain more than one URL to the content. So the URL with the greatest SEO authority is used. This is what I would expect in the OP case.

Other people sites plagiarize content so the first to publish is normally the winning URL unless the plagiarizer is a major site with lots more SEO authority. More often than not the plagiarizers don't have SEO authority and zero original content, which is where penalties begin to kick in against the scrappers plagiarizers. If a sub-domain was indexed then the main domain was indexed and the sub-domain was dropped it may feel like a penalty, but overall it is a wash.

To get both subdomain and main domain preforming well place different content on each, which is better for the visitors and better for the site. If you split your incoming link authority between a sub-domain and main domain your site ends up in a weaker position.

The subdomain should share style, or branding with the main site, not text.

Updated based on comments below

Google maps, or places, and local sites that review brick and mortar businesses are extremely helpful for sites where the only difference in the product is the location; Examples would include construction businesses, Carpeting suppliers, lumber retailers, grocery stores, etc. BBB links if available can help compete in a commodity marketplace.

  • The subdomains' content are completely different from the main site in terms of verbiage and images. The content on the subdomains are nearly identical, the main differences will be the name of the town and some random text edits, so it's basically a find and replace edit for each subdomain. The goal for the subdomains is to rank high for all the town in San Diego, and all the keywords targeted will be specific to each town.
    – John Pham
    Nov 2, 2013 at 5:40
  • If the sub-domains are nearly identical in terms of content then they can have problems competing against each other for the content which is not city name. The same problems can happen when somebody gets a site template with content and don't rewrite they just change the business name and city name - I can not find any examples right now in Google to demonstrate the results. Nov 5, 2013 at 17:26
  • The subdomians are not competing against each other since each subdomain will target a different town; this is local SEO.
    – John Pham
    Nov 7, 2013 at 21:45
  • John, my opinion on when it crosses the line is meaningless, only Google's opinion matters. And, to add, Google reserves the power to move the line as it sees fit. All I can say is that there is a line and you don't want to fall over it, regardless of if it moved or you moved. Nov 8, 2013 at 21:31
  • Note I've updated my answer based on information in the comments, I hope the new information is helpful for you. Nov 8, 2013 at 21:40

To avoid robots indexing content twice and penalizing your website, you should mention in the header or the site that must be indexed, that there exists one or more alternate versions elsewhere.

In the header of the site that duplicates information, you should mention where the original content is. We name the original content "canonical".

This technique is typically used when the mobile version of a site is on a subdomain.

Here's an example.

Assume that the desktop site is www.example.com and the mobile site is at m.example.com.

For the "page 9" of that site, we put in the header of the mobile version:

<link rel="canonical" href="http://www.example.com/index.php?id=9" />

to tell that the "main" versions is the desktop one.

In the header of the desktop version, we mention the existence of a mobile version:

<link rel="alternate" media="only screen and (max-width: 640px)" href="http://m.example.com/index.php?id=9" />

You can easily adapt this example to using two different domains names.

The important things to remember are:

  • using <link /> in page headers
  • using rel="canonical" and rel="alternate" attributes correctly. One the canonical page, you mention the alternate one, and vice versa.

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