Use Multiple Sitemaps to Monitor Different Parts of Your Site, Says Google's John Mueller.

Google’s John Mueller says that using multiple sitemaps for different parts of your site can be beneficial by allowing you to filter information in the Search Console to see how well they perform.

John Mueller was responding to a recent Reddit thread asking for the recommended sitemap size when he gave some invaluable insights.

“There is no ideal size (other than that it should be below the maximum size limits :-)). I generally recommend splitting a sitemap file into logical parts of your site so that you can monitor those parts individually (eg, category pages vs detail pages vs whatever else you have).”

Mueller suggests that your problem lies elsewhere if you have issues with Google crawling large or multiple sitemaps.

“The size & number of sitemap files generally won’t affect the crawling, unless your server is so bogged down that even fetching a handful of sitemap files would slow it down (in which case, the sitemap files wouldn’t be the problem you need to focus on anyway).”

While multiple sitemaps are useful for monitoring the different parts of your website for issues, Mueller clarified that it won’t help Google better understand your site.

“You won’t see any effect in crawlers understanding your site better. It’s purely for you to be able to monitor it better.”

Mueller continued, “It doesn’t change how Google crawls & indexes them, it’s really just so that you can track them better on your side.”

Mueller clarified that “if you filter the Search Console reports to your “category pages” sitemap file, then you can see clearer how well they perform, or if there are any problems with those pages.”

Using multiple sitemaps to diagnose indexing issues is nothing new. Marketing agency Distilled wrote a detailed guide on how to do this back in January 2011 that is still very relevant today.

It is worth noting that in November 2016, the sitemap limits were raised by Google and Bing, with Google confirming that “sitemaps & indexes can be considerably larger now” following a recent update to the sitemap protocol.

According to sitemaps.org, the following limits to sitemaps now apply:

• They have a maximum size of 50MB, although you may compress your sitemap file to help keep within limits.
• They can contain a maximum of 50,000 URLs.

You solve this by using multiple sitemaps files alongside a Sitemap index file.