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Backend OS checker·header-based fingerprint

What's running behind the curtain?

A best-effort guess at a server's operating system and stack, based only on the HTTP headers it publicly discloses — the same passive technique used by tools like Netcraft.

Passive, header-only
Confidence rated
Enter a domain to guess its backend OS.
Try github.com, wikipedia.org, or your own site.
What you get

Server fingerprinting, made transparent.

Every guess comes with a confidence level and the exact header evidence behind it — nothing is presented as certain when it isn't.

Confidence-rated guesses

Every result is labeled High, Medium, Low or No signal, so you know exactly how much to trust the answer.

Full evidence shown

See the exact Server, X-Powered-By and related headers the guess was built from — nothing is a black box.

Stack detection

We also surface likely language and framework hints — PHP, ASP.NET, Node, Python, Java — alongside the OS guess.

CDN-aware

When a site is fronted by a CDN like Cloudflare or CloudFront, we say so explicitly instead of misreporting the edge as the origin.

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FAQ

Backend fingerprinting, explained.

Many web servers voluntarily disclose their software and sometimes their OS in the Server header — e.g. "Apache/2.4.41 (Ubuntu)". Where the OS isn't explicit, some software (like IIS) only ever runs on one platform, which lets us infer it with high confidence.
Many production sites deliberately hide or omit version and OS information for security, or sit behind a CDN/load balancer that replaces the origin's headers with its own. When there's no reliable signal, we say so rather than guessing.
No. This tool only reads the headers returned by a single, ordinary HTTP request — the same information your browser receives every time you visit a site. It doesn't probe, scan, or attempt to access anything beyond that.
It means the server that answered the request is the CDN's edge node, not the origin server the site owner actually runs. The OS guess in that case describes the CDN's infrastructure, which we label clearly rather than presenting as the origin.
Yes — that's one of the most useful ways to use it. If your server is disclosing more version detail than you intended (exact OS, framework version), you can usually suppress it in your web server's configuration.