Download websites that use IIS

About IIS

A web server is the closest thing a website has to a declared allegiance. The software answering the request was installed by whoever runs the machine, not by whoever wrote the copy, and in most organisations that decision was taken once and then defended for a decade. Everything downstream follows from it, including the languages the team hires for, the database it standardises on and the identity system it authenticates against.

IIS is that kind of decision. Shipped by Microsoft since 1995 and licensed as Proprietary alongside the operating system it runs on, the server tends to appear where Windows was already the institutional default rather than where somebody compared web servers on merit. Its presence is therefore a proxy for an entire procurement posture, which is exactly why it interests people who sell into enterprises.

Version data makes that proxy sharper. As of September 2026 we see the server on 3,368,407 sites, and across them we resolve 54 distinct version strings, of which 10.0 is the reading we record most frequently. A spread that wide across a single vendor's product is not noise. The spread is the shape of an installed base that upgrades when the operating system underneath it is replaced, which happens on a procurement cycle measured in years rather than in release notes. Long tails in that distribution correspond to servers running on operating systems that reached end of support some time ago.

For a security vendor, that tail is the pitch. For a migration consultancy, the tail is a shortlist. For an independent software vendor whose product only installs on one platform, the whole population is the addressable market and the version split tells them which minimum version they can safely require. Each of those readers needs the same thing, which is not a verdict about one domain but a filtered population with countries and suffixes attached.

Geography and naming add the qualifying detail. 798,034 of the sites we detect resolve to United States, and .com dominates the suffix mix, both of which reflect where Windows hosting was sold hardest rather than any property of the software. Combine that with the other technologies we record on the same site, and the enterprise signature becomes legible, because a server of this kind sitting under a commerce platform, an analytics suite and a corporate content management system describes a very different buyer from the same server sitting alone on a parked domain.

Honesty about the method matters more here than for most detections. We read the server from response headers and from behavioural fingerprints, and headers can be suppressed, rewritten or invented. Administrators are routinely advised to remove the banner entirely, and load balancers, caches and content delivery networks frequently replace it with their own. The population we can see therefore skews toward default configurations and away from hardened ones, which means our count is a floor, and the sites most likely to be missing are the ones with the most attentive operations teams. A version string, likewise, is what the server chose to announce and not a guarantee of the binary actually running.

A per-domain lookup answers whether a single site runs this server. A downloadable list answers which sites run it, in which market, under which suffix, at which version, next to which other software. The second question is the one that supports market sizing, exposure research, migration targeting and account prioritisation, and no amount of individual lookups assembles it in time to be useful.