John Mueller: Google not index all URLS in the sitemap.xml

Do not index some pages from the site map – it is normal practice for Google. This was stated by the representative search system John Mueller during the last hangout for webmasters.

Search Console we will inform you about how much a URL has been indexed, but do not specify a particular page. This is not an issue about which to worry. For us it is absolutely normal not to index all the URL's that we find.
Only for what you need to worry - this indexing important pages on the site, which should provide site traffic, "- said Googler.

As noted by Jennifer Slegg (The SEM Post), in most cases, pages are filtered for two reasons:

• Duplicates;
• Too similar content.

In such cases it is necessary to consider the need to use rel=canonical.

Advice from SEO Hero: If you are the owner of a large site and trying to figure out why Google does not index many pages, divide the site map into multiple maps of the site to find the problem.

For example, divide the site map by type:

• Products;
• Informational pages;
• Technical pages.

This approach often helps to determine which parts of the website Google does not index, find the problem and solve it.

On site SEO Hero created three sitemaps:

• A map of all the pages;
• A map of all images;
• A map of news pages.

More detail in the material at the link - SEO Hero sitemap.