Using search engines
Search engines like Google and Bing supports various advanced search operators to refine search queries. These operators are often referred to as “Google dorks”.
We can use
site: operator in Google search to find all the sub-domains that Google has found for a domain. Google also supports additional minus operator to exclude sub-domains that we are not interested in
site:*.wikimedia.org -www -store -jobs -uk
Bing search engine supports some advanced search operators as well. Like Google, Bing also supports a “site:” operator that you might want to check for any additional results apart from the Google search. You can find all the advanced search operators Bing supports here - https://help.bing.microsoft.com/#apex/18/en-US/10001/-1