Can a sitemap index file reference sitemap files under different domains?

Question

My company owns several domain names. We also host websites for our users at their custom domains.

Our domains:

• company.com
• product1.com
• product2.com

Users's domains:

• user1.com
• user2.com

Currently, we host XML Sitemap files at the root of all of our users' websites (e.g. http://www.user1.com/sitemap.xml). These sitemap files contain all the URLs of that user's website.

To possibly improve the search engine indexing of our users' websites, we would like to start hosting a high-level, sitemap index file at the root of company.com which lists all of our users' (and preferably our products') websites' sitemap.xml files.

So something like this:

http://www.company.com/sitemap-index.xml

<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
   <sitemap>
      <loc>http://www.company.com/sitemap.xml</loc>
   </sitemap>
   <sitemap>
      <loc>http://www.product1.com/sitemap.xml</loc>
   </sitemap>
   <sitemap>
      <loc>http://www.product2.com/sitemap.xml</loc>
   </sitemap>
   <sitemap>
      <loc>http://www.user1.com/sitemap.xml</loc>
   </sitemap>
   <sitemap>
      <loc>http://www.user2.com/sitemap.xml</loc>
   </sitemap>
</sitemapindex>

According to the Sitemaps documentation on index files, it isn't possible to have a sitemap index file references sitemaps files outside of it's own domain.

Note: A Sitemap index file can only specify Sitemaps that are found on the same site as the Sitemap index file. For example, http://www.yoursite.com/sitemap_index.xml can include Sitemaps on http://www.yoursite.com but not on http://www.example.com or http://yourhost.yoursite.com.

In a different section of the same documentation, it says that it is possible to have regular sitemap files (not sitemap index files) reference URLs outside of the domain which hosts the sitemap file.

Sitemaps & Cross Submits
To submit Sitemaps for multiple hosts from a single host, you need to "prove" ownership of the host(s) for which URLs are being submitted in a Sitemap.
...
By default, this will result in a "cross submission" error since you are trying to submit URLs for www.host1.com through a Sitemap that is hosted on www.sitemaphost.com (and same for the other two hosts). One way to avoid the error is to prove that you own (i.e. have the authority to modify files) www.host1.com. You can do this by modifying the robots.txt file on www.host1.com to point to the Sitemap on www.sitemaphost.com.

My question(s):

• First of all, Can this 'workaround' for cross-submits work with sitemap index files as it does with normal sitemap files? I don't want to go through the effort to implement it without knowing it is even possible. Unfortunately, the documentation doesn't say either way.
• Second, is what I am attempting even a good idea? We want to boost SEO for all of the websites we manage. We think linking the sitemaps together will help but we are not sure. Does anyone have any experience with complicated sitemaps and index files who are willing to share their experience?

Solution 1

As far as Google is concerned, it is possible to make "cross site submissions" of XML sitemaps if you are a "verified owner of the sites" (e.g. have proven your ownership in the Google Webmaster Tools).

You could - for example - as well place all sitemaps on company.com.

See this google help page for detailed instructions: Simplify multiple sitemap management

For your second question: Sitemaps are a good thing for indexing (if done right, so you should watch out for errors). In some cases (say, if you are webmaster of a news site) your ranking depends on how fast Googlebot picks up freshly published pages. So, sitemaps are no general ranking factor, but far from being useless for your rankings.

Solution 2

As you already aware of google sitemap guidelines, i won't dig more into it. Based on my experience, i don't think you can keep other domain's sitemap at your main domain.

I am completely agree with your above comment. it is not necessary to have sitemap file for improving search engine rankings. It just help search engine crawlers to find pages on your website easily.

Comments

[Jesse Webb]

Although old (from 2008), this Google Webmasters FAQ about Sitemaps may anwser my second question about boosting SEO. It claims that using sitemaps file not improve SEO rankings, they simply help SEs discover pages which might not be normally crawled (e.g. because they are behind a form or for whatever reason).