All
search.google.comFree
search.google.com allows you to index your website.
Go to search.google.com/...
OpenGraphFree
OpenGraph allows a better referencing and a better visual on social networks.
Go to ogp.me
alyze.infoPaid offers
alyze.info allows you to know the referencing errors in order to correct them.
Go to alyze.info
sitechecker.proPaid offers
sitechecker.pro allows you to have a score on the referencing of your site and to show some points to improve.
Go to sitechecker.pro