It has all entries released in USA, including official, unlicensed, protos and compilations. World unlicensed games like Xeno Crisis and others aren't included and will have their own database later.
It's heavily based on @SupraKarma's improvements on the official or development database that was created here in the HS forums, I've added three missing entries MTV's Beavis and Butthead (USA), Prince of Persia (USA), Outback Joey (USA) and 22 titles released on the Sega Channel service, which are exclusives, even some undumped titles and those that were only available physically in Europe, Japan and Brazil.
Early prototypes which are mostly broken/incomplete weren't considered, while the most complete ones were already tested and added on previous efforts.
3D Box art: