Emoji come from the claimed OS's emoji font
Under a Windows claim the flag measures about as wide as its two letters (a ratio above 0.8); under a macOS or Android claim it ligates (a ratio below 0.7). N/A under a Linux claim and on engines that bundle their own emoji font (severity: warn).
What a detector infers
Emoji are drawn from the operating system's colour emoji font, and the fonts differ in a way measureText can see without rendering a pixel. Segoe UI Emoji on Windows does not join a pair of regional-indicator letters into a flag — Windows shows the two letters — while Noto Color Emoji on Linux and Android and Apple Color Emoji on macOS ligate the pair into one flag glyph.
So the width of the US flag divided by the widths of its two letters is about 1.0 on Windows and well below 1 elsewhere: measured 1.0 on Chrome and Edge on Windows and 0.624 on genuine Linux Chrome, which kept that value while claiming Windows. Because it is a ratio of two measurements in one font, browser zoom cannot move it, and ligation is a property of the font file rather than of the browser.
The emoji's own advance is read as supporting evidence: 1.373 em in Segoe UI Emoji against 1.248 em on Linux. In the audit's corpus, 173 of 189 Windows visitors fall in one emoji-width cluster, three visitors claiming Windows have Linux or macOS widths, and five Android or macOS visitors have the Windows width. Where emoji-surface-vs-realm only asks whether two realms agree, this row asks whether the font matches the claimed OS.
Firefox bundles its own emoji font, which draws flags on Windows too, so the Windows rule applies to Chromium browsers.
How to resolve it
Emoji come from the font the operating system supplies, below anything a user-agent override reaches. Present the OS the browser runs on; overriding measureText cannot fix it, because the score is a ratio of two widths from the same font.
Nearby checks in Network & WebRTC
- navigator.connection.downlink sits on Chrome's 50 kbps grid, capped at 10
downlink-on-50kbps-gridnavigator.connection.downlink is not a raw measurement. Blink's NetworkStateNotifier multiplies the network-quality estimate by a per-host… - A server-reflexive candidate only appears when a STUN server answered
srflx-only-from-answering-stunA server-reflexive (srflx) ICE candidate is the public address a STUN server reports back in its reply to a binding request. - Every server-reflexive address is one the STUN server actually handed out
srflx-was-seen-by-stunA server-reflexive candidate exists only after a STUN server received a binding request from that public address and replied with it. - Canvas text is anti-aliased the way the claimed OS rasterises it
glyph-aa-levels-vs-osCanvas text is rasterised by the platform's font engine, and the engines leave different fingerprints in the alpha channel. - The default monospace font is the claimed OS's
monospace-default-vs-osThe generic monospace family resolves to a font the platform chooses. - The JS heap ceiling fits the memory the browser reports
heap-ceiling-vs-device-memorynavigator.deviceMemory and V8's heap ceiling, performance.memory.jsHeapSizeLimit, look unrelated but are computed from the same number: the… - The address WebRTC exits from matches the address this page was served to
webrtc-ip-vs-connectionThis is the one check on this page that cannot be answered from inside the page, and the only one that makes a network call. - Relay-forced WebRTC exits the same address this page arrived from
webrtc-turn-egressEvery other WebRTC check on this page reads what the browser is willing to show it.
Clearcote is a browser built for fingerprint coherence
It is a Chromium fork, maintained by the same people who wrote this reference. It ships as a compiled browser rather than as a stealth script injected into someone else's — which is a description of how it is built, and is not an argument about how it behaves on this check.
This audit takes no position on how Clearcote scores on Network & WebRTC checks, on this one, or anywhere else. It has no baseline corpus of other people's fingerprints to rank you against and no vendor scoreboard — nearly every check is self-referential, asking one browser the same question through two independent APIs and reporting whether both answers can be true at once. It runs identically on any browser, including ours. Run it on yours and read the result yourself.
See the other checks in Network & WebRTC — the family emoji-font-vs-os belongs to.