In many cases you can, but there's never a guarantee that a given IP address will have reverse DNS records configured for resolve it into. On top of that, if it's a major site it's likely hosted behind a content delivery network that may a share a single IP address across thousands or even millions of completely unrelated servers. Cloudflare does some pretty interesting stuff with that approach: https://blog.cloudflare.com/cloudflare-servers-dont-own-ips-anymore/ edit: bad at typing