The browser's own UI strings are in the language Intl resolves
The validationMessage of an empty required field is in the same language as the Intl default locale. N/A for messages without a table entry and outside the Google Chrome brand (severity: warn).
What a detector infers
The messages a browser writes itself — 'Please fill in this field.' under an empty required input — come from the renderer's resource bundle, loaded in the UI locale. That is the same locale Chrome sets as ICU's default, so validationMessage and Intl speak the same language on an unmodified browser. Locale emulation moves only one of them: the DevTools protocol's locale override changes ICU's default and leaves the resource bundle where it was.
Measured on genuine Chrome with Turkish, Spanish, French, German, Estonian, Korean and British English UI locales: every message in the matching language. Under Playwright's locale 'de-DE', Intl resolved de-DE while the required-field message read 'Please fill in this field.' The comparison is by language, using a small table of each language's message — English alone has two, 'fill out' for en-US and 'fill in' for en-GB — and a message outside the table reads N/A.
The table holds Google Chrome's wording, so other brands are N/A. Neither Accept-Language nor navigator.languages is involved. chrome-headless-shell carries only English strings whatever --lang says, so its messages are English under any locale.
How to resolve it
Set the language at launch — --lang on Windows, LANGUAGE or LANG on Linux — rather than through a locale override. The override changes Intl and nothing else, so the browser's own strings keep announcing the real UI language.
Nearby checks in Environment & locale
- Exactly one voice is the default, and it is the first
voice-default-is-firstChromium assembles one voice list — the operating system's voices first, then extension voices such as Google's network voices — and marks… - Google's network voices arrive as Google's exact set
google-voices-exact-setBranded Google Chrome on Windows, macOS and Linux adds a set of network voices from a component extension whose manifest lists exactly 19 of… - The local voices come from the claimed OS's speech engine
local-voice-vendor-vs-osVoices marked localService are the host's own speech engine, enumerated by the browser from the operating system, and their names say where… - Intl's default locale is a UI locale desktop Chrome ships
intl-is-a-chrome-ui-localeChrome's Intl default locale — what new Intl.DateTimeFormat().resolvedOptions().locale returns — is not the operating system's region. - MediaCapabilities powerEfficient agrees with WebCodecs prefer-hardware
power-efficient-vs-webcodecsMediaCapabilities.decodingInfo() reports whether decoding a format would be power-efficient, and WebCodecs' VideoDecoder.isConfigSupported()… - A playback AudioContext buffers more than an interactive one
playback-hint-buffers-moreAn AudioContext created with latencyHint 'playback' asks for a larger buffer than one created with 'interactive', and Chrome honours the… - AudioContext latencies are values Chrome's audio stack can produce
audio-latency-render-stateTwo AudioContext latencies are produced by the audio stack at particular moments, and their values are constrained in ways a constant is… - A granted geolocation fix carries a real accuracy
geolocation-has-accuracyEvery position a real location provider returns comes with an accuracy: the radius, in metres, within which the true position probably lies.
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 Environment & locale 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 Environment & locale — the family validation-message-vs-intl belongs to.