With Google sitelinks search box, people can reach your content more quickly from search results.
https://developers.google.com/webmasters/richsnippets/sitelinkssearch?utm_source=wmc-blog&utm_medium=direct-referral&utm_campaign=sitelinks-searchbox
Widgets · Site Search
Get access to data on 14,294,716 websites that are Sitelinks Search Box Customers. We know of 2,000,002 live websites using Sitelinks Search Box and an additional 12,294,714 sites that used Sitelinks Search Box historically and 1,044,993 websites in the United States.
Get a list of 14,294,716 websites using Sitelinks Search Box which includes location information, hosting data, contact details, 2,000,002 currently live websites and an additional 1,950,956 domains that redirect to sites in this list. 12,294,714 sites that used this technology previously and 1,044,993 websites in the United States currently using Sitelinks Search Box.