I recently wrote a post about the maximum number of URLs [or maximum file size] of a sitemap that Google support. In that post, I mentioned the sitemap index file which we can create in case our sitemap has reached 50,000 URLs or if the size of the sitemap file has reached a size of 10MB.
What actually is a sitemap index file?
Sitemap index file contains URLs to different sitemaps. It does not have URLs of pages: instead, it will point to different sitemaps that you may create. Once your sitemap reaches the limitations which I mentioned above: you can then create another sitemap and in order to submit multiple sitemaps to SEs, you can simply make a sitemap index file and then submit it. As it will contain URLs of all the sitemaps, SEs will download all the sitemaps and you don’t have to submit each sitemap separately.
Here is a sample sitemap index file:
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<sitemap>
<loc>http://www.yoursite.com/your-sitemap-number-one.xml</loc>
</sitemap>
<sitemap>
<loc>http://www.yoursite.com/your-sitemap-number-two.xml</loc>
</sitemap>
</sitemapindex>
