Be aware that this site doesn't do what it claims: "See which web sites are sharing the same IP Address." The truth would be: "See which web sites that have previously been searched for on our site that shares the same IP"<p>Basically it will only show sub-domains within the domain you search for, unless previous searches for other domains happen to match the IP.<p>I tested this just to confirm: I searched for one of my domains (apr. 20 domains on the same IP) and only sub-domains showed up. I searched for another of my domains and the sub-domains+my previous search showed up.
It was unable to detect any other website on my server, YouGetSignal I use a lot, and works well.<p><a href="http://www.yougetsignal.com/tools/web-sites-on-web-server/" rel="nofollow">http://www.yougetsignal.com/tools/web-sites-on-web-server/</a>
Bing/MSN Search had this for ages in the form of query "ip:IP_OF_THE_SERVER" which would return a list of indexed websites having domains with this IP address.<p>I suspect this site uses Bing under the hood - finds the IP of entered website domain, queries bing and returns the results.<p>This is widely used by security folks when doing pen testing - even if you don't find any flaws on the targeted website, there's a great chance other websites won't be as secure if it's on shared hosting and such tools help to find those other websites.
I use <a href="http://spyonweb.com/" rel="nofollow">http://spyonweb.com/</a>, which shows sites on the same IP address, using the same DNS servers, adsense publisher, or Google analytics account.
It has some cool options too. For example:<p><a href="http://sharingmyip.com/?site=ycombinator.com" rel="nofollow">http://sharingmyip.com/?site=ycombinator.com</a><p>It finds related sub-domains being used, like wiki.ycombinator.com<p>Or for Cisco:
<a href="http://sharingmyip.com/?site=cisco.com" rel="nofollow">http://sharingmyip.com/?site=cisco.com</a><p>It shows that some of their external domains are pointed to internal addresses (in the 10.0 range).
Note that if a site is using a CDN like Akamai, the results may show some strange bedfellows and will be entirely dependent on the location of the host doing the lookup. Don't make the assumption that they're in any way related to each other or even that the authoritative origins are in the same hosting facility. Nice tool, though, does what it says and could be a useful check whenever you're considering implementing some draconian firewall rules.
In modern distributed architectures, you might see a lot of completely unrelated sites on the same IP.<p>I used to work at one of the major CDNs, and we spent a lot of effort segregating some of our customers into separate IP space, so they wouldn't cause the rest of our customers to get firewalled by the likes of China.
Or that the owner of symbolics. com (first domain ever) <a href="http://sharingmyip.com/?site=symbolics.com" rel="nofollow">http://sharingmyip.com/?site=symbolics.com</a><p>Also owns iblog. com, tablets. com, etc.
Another one:<p><a href="http://sharingmyip.com/?site=facebook.com" rel="nofollow">http://sharingmyip.com/?site=facebook.com</a><p>They have dev . facebook.com pointing to 10.30.0.50 (internal IP address).
Not that anyone probably cares, but it doesn't work for domains that only have an IPv6/AAAA record. An interesting option there might be to see sites that share an IPv6 prefix of a certain length?
I can't do much about 4 domains pointed to one IP and handled by apache vhosts config. But the good thing it does is that it co-relates previous searches to build its DB.<p>That's quite better than fail actually, it understands that the user is trying to test me :), in turn it benefits.<p>But definitely no results for first timers. Multiple sources (gps, wifi) could be used to build out a cell-id -> location DB in similar way.