shell.windows.comは安全ですか？

Microsoft's site for recognizing different file types/extensions. If You're looking for a definiton of some less than well-known extension, this page probably won't help You; it seems to be able to tell the file type from extension for only those types that are pretty well-known, and in Windows environment. *nix file types, not to mention Mac's files, get usually no explanation, nor do the more exotic ones. Some Google Ads -type ads, otherwise just a plain, bare page with some info (or, more often, none) and some links. No malware present, trustworthy.