"SEO indexing is not a big deal anymore! There are many tools available to help you determine if a site is being indexed.
Indexing is, at its core, a page-level process. In other words, search engines read pages and treat them individually.
A quick way to check if a page is being indexed by Google is to use the site: operator with a Google search. Entering just the domain, as in my example below, will show you all of the pages Google has indexed for the domain. You can also enter a specific page URL to see if that individual page has been indexed. If your site or page is not being indexed, the most common culprit is the meta robots tag being used on a page or the improper use of disallowing in the robots.txt file.
Both the meta tag, which is on the page level and the robots.txt file provide instructions to search engine indexing robots on how to treat content on your page or website.
The difference is that the robots meta tag appears on an individual page, while the robots.txt file provides instructions for the site as a whole. On the robots.txt file, however, you can single out pages or directories and how the robots should treat these areas while indexing."