Will sitemaps (with indexes and text url lists) work with cross subdomains? - sitemap

Question

I have two subdomains I use for my website: static.example.com and www.example.com. Due to the nature of my web server, it is best for me to serve the static content (css, js files and hopefully sitemaps) with static.example.com.
I have put Sitemap: https://static.example.com/sitemap.xml into the robots.txt for www.example.com. However, I will need to have several sitemap indexes with hundreds of thousands to a few millions of urls under different subdirectories.
For example, I have the following subdirectories in the main website:
www.example.com/articles
www.example.com/questions
www.example.com/videos
...
Therefore, can I structure my sitemap.xml in this way:
<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<sitemap>
<loc>https://static.example.com/sitemaps/article.xml</loc>
</sitemap>
<sitemap>
<loc>https://static.example.com/sitemaps/question.xml</loc>
</sitemap>
<sitemap>
<loc>https://static.example.com/sitemaps/video.xml</loc>
</sitemap>
</sitemapindex>
Then for example in the article sitemap:
<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<sitemap>
<loc>https://static.example.com/sitemaps/article/1-10000.txt</loc>
<lastmod>2021-04-22T19:50:00+00:00</lastmod>
</sitemap>
<sitemap>
<loc>https://static.example.com/sitemaps/article/10001-20000.txt</loc>
<lastmod>2021-04-22T19:50:00+00:00</lastmod>
</sitemap>
</sitemapindex>
And in each .txt files I will be listing the urls that address the main website. For example
https://www.example.com/article/1
https://www.example.com/article/5
https://www.example.com/article/8
...
Is this structure okay? Cross submits explained here explicitly allows me to put my main sitemap under a different domain and for txt url lists it tells me to put them into the highest-level directory. Didn't see it mentioning serving url lists or sitemap indexes under a different subdomain.
Is it possible for me to serve my sitemaps and url lists in this way?

Answer 1

This by default won't work. The sitemaps protocol states that (see section on "Sitemap file location
"):
Note that this means that all URLs listed in the Sitemap must use the same protocol (http, in this example) and reside on the same host as the Sitemap. For instance, if the Sitemap is located at http://www.example.com/sitemap.xml, it can't include URLs from http://subdomain.example.com.
However, there are ways to make it work. For example, with Google, it will work as long as all subdomains have been verified in Search Console (see details here). More generally, you need to edit the robots.txt files to prove that you own all these hosts (even if they are just subdomains). You can see the "Sitemaps & Cross Submits" section of the same sitemaps protocol for details.