Really Simple Discovery is a way to help client software find the services needed to read, edit, or "work with" weblogging software.
https://cyber.law.harvard.edu/blogs/gems/tech/rsd.html
Syndication Techniques
Get access to data on 54,806,636 websites that are Really Simple Discovery Customers. We know of 30,806,438 live websites using Really Simple Discovery and an additional 24,000,198 sites that used Really Simple Discovery historically and 3,267,183 websites in the United States.
Get a list of 54,806,636 websites using Really Simple Discovery which includes location information, hosting data, contact details, 30,806,438 currently live websites and an additional 1,989,193 domains that redirect to sites in this list. 24,000,198 sites that used this technology previously and 3,267,183 websites in the United States currently using Really Simple Discovery.
Countries
Financial
Group
Region