# Why the User-Agent says Windows 10 on Windows 11 > Windows 11 and 10 both send Windows NT 10.0 in the User-Agent. Only the platformVersion client hint, 13 or higher, says Windows 11. Source: https://mosaicbrowser.com/blog/windows-11-user-agent-windows-10 ## Why the User-Agent says Windows 10 on Windows 11 Windows 11 and 10 both send Windows NT 10.0 in the User-Agent. Only the platformVersion client hint, 13 or higher, says Windows 11. ![Windows 10 versus Windows 11, each name in its own tile: Two versions of Windows, one string](https://mosaicbrowser.com/covers/windows-11-user-agent-windows-10.webp) The User-Agent says Windows 10 on Windows 11 because both systems send the same token, `Windows NT 10.0`, and nobody changed it for Windows 11. The string cannot tell the two apart. The real version is in a client hint, `Sec-CH-UA-Platform-Version`, and a major version of 13 or higher there means Windows 11. So when a site or a log file reports "Windows 10" for a Windows 11 machine, it is usually reading the User-Agent and nothing else. Your system is fine. ## The User-Agent on Windows 10 and Windows 11 Chrome on either system sends a User-Agent like this: ``` Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/.0.0.0 Safari/537.36 ``` `Windows NT 10.0` is the kernel version token Windows 10 introduced. Microsoft's own guidance for Edge says the User-Agent will not be updated to tell Windows 11 from Windows 10, and Chrome's reduced User-Agent freezes the platform part of the string anyway. That is the same reason every Mac's Chrome claims `Mac OS X 10_15_7` whatever macOS it runs ([the macOS version of this story](https://mosaicbrowser.com/blog/mac-os-x-10-15-7)), and why the version after the Chrome major is always `0.0.0`. Firefox does the same with its own string. It sends `Windows NT 10.0` on both systems. Mosaic is a desktop app Email yourself the link and open it on your computer. [How it works: Machines that exist](https://mosaicbrowser.com/features/real-fingerprints) ## The client hint that tells them apart In Chromium browsers, which include Chrome and Edge, the version lives in a high-entropy client hint, so a site has to ask for it. A server asks with a response header: ``` Accept-CH: Sec-CH-UA-Platform-Version ``` The browser sends `Sec-CH-UA-Platform-Version` on later requests to that site. The first request never carries it, because the browser did not know yet that the site wanted it. A page can also ask from JavaScript: ``` const { platform, platformVersion } = await navigator.userAgentData.getHighEntropyValues(['platformVersion']) const major = parseInt(platformVersion.split('.')[0], 10) // platform === 'Windows' and major >= 13: Windows 11 // 1 to 12: Windows 10 // 0: older than Windows 10 ``` On Windows the number is not the marketing version. It comes from the `Windows.Foundation.UniversalApiContract` version, which is why Windows 11 shows up as 13, 14, 15 and so on rather than 11. Microsoft's detection sample uses the rule above: 13 or higher is Windows 11. Recent Windows 10 releases report `10.0.0`. ([What getHighEntropyValues returns](https://mosaicbrowser.com/blog/gethighentropyvalues-explained) lists the other values the same call can read.) ## Why this matters to a profile that claims Windows A browser profile that claims Windows has to get the hint right, because the string gives it nothing to get wrong. Every real Chrome on Windows sends the same `Windows NT 10.0`, so a hand-written string that says `Windows NT 11.0` marks itself at once. No shipping Chrome sends that. The hint is where the version claim actually lives, and where a careless spoof shows. Three ways we know of: 1. The hint is missing. Chrome's DevTools call `Emulation.setUserAgentOverride` replaces the string and, unless it is also given the metadata, drops the client hints that go with it ([setUserAgentOverride clears the hints](https://mosaicbrowser.com/blog/setuseragentoverride-clears-hints)). 2. The hint is set in the page and not in its workers. `platformVersion` can be read from a service worker, and script injected into the page does not reach that realm. A page saying 15.0.0 while its worker reports the host's own version is two answers from one browser. 3. The hint disagrees with the rest of the machine: a Windows 11 claim on a profile whose GPU, screen or fonts do not belong to a Windows PC. ## What Mosaic draws When Mosaic's generator draws a Windows profile, the User-Agent says `Windows NT 10.0` whichever version it claims, because that is all a real Chrome says. The version goes in the platform version alone. Windows 11 profiles get `15.0.0` or `14.0.0`, Windows 10 profiles get `10.0.0`, and the draw leans towards Windows 11. The value reaches the browser as an engine switch, `--fingerprint-platform-version`, and Tesseract Chrome, our own Chromium, applies it in C++. So the page, its iframes and its workers read one number, and the header carries the same one. Nothing is patched with injected JavaScript ([real fingerprints](https://mosaicbrowser.com/features/real-fingerprints) describes how a profile's hardware is drawn). One limit, stated plainly: fonts and how text is rasterised come from the computer the browser runs on, and no switch reaches them. A profile always matches best on the operating system its computer actually runs. ## Questions ### Why does my User-Agent say Windows NT 10.0 on Windows 11? Because the string was never changed for Windows 11. Windows 10 and Windows 11 both send Windows NT 10.0, so the User-Agent cannot tell them apart. Nothing is wrong with your browser or your system. ### How can a website tell Windows 11 from Windows 10? By asking for the platform version client hint. A server sends Accept-CH: Sec-CH-UA-Platform-Version and reads the header on later requests, or a page calls navigator.userAgentData.getHighEntropyValues(['platformVersion']). A major version of 13 or higher means Windows 11. ### Does Firefox tell sites it is on Windows 11? Firefox has not shipped User-Agent Client Hints, so it has no platformVersion to send, and its User-Agent says Windows NT 10.0 on both systems too. A site cannot tell Windows 11 from Windows 10 in Firefox from the headers. ### What platformVersion does Windows 10 report? A major version from 1 to 12, taken from the Windows UniversalApiContract version. Recent Windows 10 releases report 10.0.0. A value of 0 means a Windows release older than Windows 10. ## Related [Why every Mac's Chrome says Mac OS X 10_15_7](https://mosaicbrowser.com/blog/mac-os-x-10-15-7): Chrome froze the macOS version in its User-Agent, so every Mac claims 10.15.7. The real one is in Sec-CH-UA-Platform-Version, a hint sites must ask for. [getHighEntropyValues: what a page can ask for and what it gets](https://mosaicbrowser.com/blog/gethighentropyvalues-explained): getHighEntropyValues hands a page architecture, bitness, model and full versions on request, and each answer must match the headers Chrome sends. [setUserAgentOverride without metadata wipes your client hints](https://mosaicbrowser.com/blog/setuseragentoverride-clears-hints): Without userAgentMetadata, setUserAgentOverride left our page with empty brands while a worker reported both. We set the User-Agent at launch instead. [Why Chrome's User-Agent says 0.0.0](https://mosaicbrowser.com/blog/chrome-user-agent-0-0-0): Chrome zeroes everything after the major, so the User-Agent says 0.0.0 and the build moves to Sec-CH-UA-Full-Version-List. A real build in the UA is a tell. [Machines that exist: fingerprints drawn from real hardware](https://mosaicbrowser.com/features/real-fingerprints): Mosaic draws each profile's GPU, screen, CPU, memory and fonts from one real device, so the parts of a fingerprint agree with each other and with the host. [Privacy Sandbox is retired, and its APIs are a version tell](https://mosaicbrowser.com/blog/privacy-sandbox-apis-removed): Chrome is removing Topics and Protected Audience release by release, so whether runAdAuction exists tells a page which Chrome you really are. [Accept-CH and Critical-CH: how a server asks for more](https://mosaicbrowser.com/blog/accept-ch-critical-ch): Accept-CH asks Chrome for more client hints on the next request; Critical-CH makes it retry the first. A server sees both requests and can compare them. [Not_A Brand: how Chrome's GREASE brand is computed](https://mosaicbrowser.com/blog/not-a-brand-grease): The Not A Brand entry in Chrome's user agent is computed from the major version by a fixed formula, so a label that doesn't fit the claimed major is a tell. ## Mosaic, on your own computer The browser this blog is about: its own Chromium, fingerprints from real machines and a proxy exit per profile. Free holds 3 profiles. Pro is $49 a month for any number. Mosaic is a desktop app Email yourself the link and open it on your computer.