There are several common reasons a URL might not be indexed:
- The URL doesn't exist or returns an error status when Google tries to crawl it.
- The content of the URL is a duplicate of a page that Google has already crawled.
- The contents of the URL are too large (for example, a large PDF).
- Your available quota isn’t enough to cover all the URLs in the Sitemap you're submitting for indexing. If you’re requesting indexing of URLs in a Sitemap, you can use the
<priority>tag to help Google understand which URLs are more important and should be prioritized for indexing. More information about creating a Sitemap.
It's also possible that your Sitemap has an error. You can use Webmaster Tools to see any problems Google encountered when crawling URLs in your Sitemap.