the available screen area fits inside the screen
Check id screen-avail-within-bounds
What an ordinary browser yields
availWidth is at most width and availHeight is at most height — the usable area fits inside the display, with the difference being the taskbar or dock.
What a detector infers
The available screen area is a subset of the screen by definition: availWidth and availHeight describe what is left of width and height after the operating system reserves space for its own chrome, a taskbar or a dock. So the available area is bounded by the screen it belongs to, always, on every windowing system. There is nothing to know about the host to check this — it is true by construction, which makes it one of the cheapest hard invariants available. What breaks it is a spoof that sources the screen size and the available size from different places, or randomises one per launch without re-deriving the other; the result is a usable area larger than the display it sits on, which no compositor can present. This check ships on the strength of that invariant alone — it carries no sighting, because the stealth browsers measured here all re-derive the available area correctly from whatever screen they draw, and a check with nothing to report should report nothing rather than hedge. Only the DIMENSIONS are asserted, never the origins: availLeft and availTop are expressed in virtual-desktop coordinates and are legitimately negative or larger than the screen height on a multi-monitor setup, measured at availLeft -104 and availTop 1440 on an ordinary Chrome here, so asserting on those would fail every multi-monitor user.
How to resolve it
Derive the available area from the same screen definition as the screen size rather than setting the two independently. A randomised screen paired with a fixed available size eventually produces a usable area bigger than the display, and that combination is impossible rather than merely unusual.
Nearby checks in Screen & display
- screen.width/height backed by the display (matchMedia)
screen-matchmediaThis check reads window.screen.width/height, then asks the CSS media-query engine the same question via matchMedia("(device-width: Npx) and… - devicePixelRatio matches matchMedia resolution
dpr-matchmediaThe check compares window.devicePixelRatio against the layout engine's own answer, querying matchMedia with a min-resolution/max-resolution… - screen dimensions are a plausible physical size
screen-plausibleA pure sanity range on screen.width and screen.height: both must be at least 200px and no more than 16384px. - screen.colorDepth decomposes into the CSS color media feature
color-depth-vs-media-colorscreen.colorDepth and the CSS color media feature describe one display in two different units: total bits per pixel, and bits per colour… - screen has an OS chrome inset (avail < screen on either axis)
taskbar-presentscreen.availWidth/availHeight describe the area left over after the OS reserves space for its own chrome — a Windows taskbar, a macOS dock… - the outer window fits within the screen
window-boundsThe check asserts only the zoom-invariant bound: window.outerWidth/outerHeight must be non-zero and must fit within the screen. - a non-touch desktop has a fine pointer + hover
pointer-hover-desktopThis check applies only when the UA identifies a desktop platform (Windows, Macintosh, Mac OS X, X11, Linux, CrOS, and not Android/Mobile)… - maxTouchPoints coheres with pointer media
touch-pointer-coherenceA one-directional coherence test: if navigator.maxTouchPoints is greater than zero, matchMedia("(any-pointer: coarse)") is expected to…
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 Screen & display 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 Screen & display — the family screen-avail-within-bounds belongs to.