Who Is Hosting This Website
The addresses a site resolves to, the network that holds them, and what its headers give away about the CDN and the stack in front of it.
This tool needs JavaScript: the server makes the request, because a browser cannot read another site headers.
A domain or a URL. One request is made to the home page over https, the same request a browser would make.
This is one of the few tools here that asks the server rather than your browser, because a browser cannot do it. Nothing you put in is stored; the request is rate limited by address and the answer is not cached.
Where a site actually lives: the addresses it resolves to, the network those addresses belong to, and what the response headers give away about what is in front of it.
The honest answer is often “Cloudflare”, and that is worth knowing too. A CDN is designed to be the thing you see, and no lookup from outside can see past a correctly configured one.
How to use
Put in a domain or a URL. One request is made to the home page over https, which is the same request a browser would make. Nothing else is probed.
Example
Host wordpress.org
Addresses
198.143.164.252 no PTR record
Network holding 198.143.164.252
name AUTOMATTIC
range 198.143.164.0 – 198.143.164.255
country US
organisation Automattic Inc
What the site says about itself
status 200
final address https://wordpress.org/
server nginx
in front nothing that announces itself, so this is probably the origin
looks like WordPress, from the headers it sendsPitfalls
A CDN hides the host, deliberately. With Cloudflare, Fastly or CloudFront in front, the address and the network you see belong to the CDN. The origin is visible only when it is misconfigured, and building anything on that is building on somebody else’s mistake.
Shared hosting looks like the host, not the site. On shared infrastructure every site on the box has the same address and the same headers, which tells you the provider and nothing about the account.
Server and X-Powered-By are whatever the server chooses to say. They are often removed, sometimes
wrong on purpose, and X-Powered-By: PHP/7.4 is a gift to anybody scanning for old versions. Removing
it is one of the cheapest hardening steps there is.
Reverse DNS is a hint, not a fact. A PTR record says what the address owner chose to write there. Matching it against forward DNS is what makes it meaningful, and most addresses have no PTR at all.
Several addresses usually means a CDN or a load balancer, not several servers you could reach. The one your browser uses depends on where you are, which is the point.
This is passive. One GET to the home page, the same one a browser makes. It does not scan ports, probe paths or test for vulnerabilities, because doing any of that to a site you do not own is a different activity with a different legal status.
Hosting reviews built on this data are usually wrong. Response time from one server in one place says nothing about the experience of the people who actually visit the site.
Compatibility
Three lookups: DNS for the addresses, RDAP for the network that holds the first of them, and one HTTPS GET to the site. This is one of the few tools here that asks the server, because a browser cannot read another origin’s response headers and cannot make a DNS query at all.
The network lookup uses ARIN’s RDAP service, which redirects to the other regional registries for addresses outside its own region; the redirect is followed by the same guard as everything else.
That guard matters more here than anywhere: this tool takes an address from a stranger and asks the server to fetch it. Only http and https, only on the standard ports, the name resolved before use with every address checked against the private and reserved ranges, redirects followed by hand with the checks repeated on each hop, and the response capped in size and time. The request is rate limited to 20 a minute per address and nothing is stored.
CDN detection is by header, and the header that proved it is named: cf-ray for Cloudflare,
x-vercel-id for Vercel, x-amz-cf-id for CloudFront, x-served-by for Fastly, and so on. Where
nothing announces itself the tool says so rather than guessing.