This SEO technique is very useful if you have been hit by a penalty and want to identify what pages to remove from your site. Obviously, you don’t want to do this for pages that are still getting traffic from elsewhere, but removing certain pages (and links going towards them) with zero visitors can only help your Google rankings.
Traditionally, we would go to Google Search Console and look at the “Indexing” -> “Pages” -> “View data about indexed pages”, to see what pages Google currently indexed. The problem is that this method is inaccurate, because Google is slow to update this info in the Search Console. And if you have been hit by a penalty, you probably want pages removed FAST.
Another method that was used is to do a Google search for site:https://www.domain.com/page/ and to see if it shows up. The problem with this method is that it will show URLS that Google is aware of, but may not be in the main index.
To figure out what pages Google really doesn’t want in its index, do a search for “domain com PAGE TITLE” (without brackets, if your domain is domain.com with the space in between domain and com). If your page doesn’t show up anywhere in the SERPS, that means that Google really doesn’t want that page in it SERPS, and is very unlikely that it will put that page back in the main index again (as I tested it). “PAGE TITLE” doesn’t even have to be the full page title, just the most important part that is unique to that page as illustrated in with this example of our site:
This method can be tedious if not automated, but can be prioritized with pages that get no visitors at all (do a Screaming Frog crawl connected to GA)