getBoundingClientRect === Range client rects
Check id bcr-vs-range
What an ordinary browser yields
Both APIs return the same left value, and both sit on the 1/512 grid.
What a detector infers
Two independent APIs are pointed at the same laid-out text: an absolutely-positioned div containing "WWWWWiiiii" is measured with element.getBoundingClientRect().left, and a Range selecting the same node contents is measured with getClientRects()[0].left. Both read out of the same layout tree, so on an unmodified browser they agree exactly and both land on the 1/512 grid — the check passes only when the two lefts agree within 1e-6 AND both are on-grid. That double condition catches two distinct situations: a hook that perturbs getBoundingClientRect (a common way to fuzz element geometry) rarely also covers Range client rects, so the readings contradict each other; and a scaled value fails the grid test even if both paths were covered. N/A if the probe could not produce both rects.
How to resolve it
Don't perturb rect geometry from JavaScript. If element geometry must vary, it has to vary in layout itself so every rect API reads from the same tree and stays quantised — otherwise the two readings of one element disagree, which no real rendering produces.
Read in the wild by
CreepJS
CreepJS — an open-source research demo, not a production detector — registers both sides of this pair for tamper-testing in src/lies/index.ts: `searchLies(() => Range, { target: ['getBoundingClientRect','getClientRects'] })` and `searchLies(() => Element, …)` with both methods in its target list, alongside `searchLies(() => DOMRect)` and `searchLies(() => DOMRectReadOnly)`. What that code does is check whether those rect methods have been hooked or poisoned — it does not read the geometry or compare the two readings against each other; the cross-API comparison on this line is ours. The overlap worth noting is narrower: an independent research project arrived at the same two rect surfaces as the ones worth watching.
CreepJS src/lies/index.ts: `searchLies(() => Range, { target: ['getBoundingClientRect','getClientRects'] })`; `searchLies(() => Element, { target: ['append','appendChild','getBoundingClientRect','getClientRects','insertAdjacentElement', … ] })`; `searchLies(() => DOMRect)`; `searchLies(() => DOMRectReadOnly)`. Signature: `searchLies: (fn: Function, config?: SearchConfig): void` — tests prototype methods for tampering (toString tampering, getter poisoning, proxy obfuscation), not geometry values.
Every attribution traces to a published artifact. See the sources and their limits.
Nearby checks in Render & GPU
- text metrics are not a uniform multiple of the engine's own grid
text-metrics-uniform-scaleThis is the sub-pixel grid check asked one question deeper. That check reports THAT widths have left Blink's 1/512-pixel grid; this one asks… - N copies of a glyph measure exactly N times one copy
text-advance-additivityThe advance width of N copies of a single glyph is exactly N times the advance of one copy. - ink extent and advance width grow by the same step
text-ink-extent-vs-advanceTextMetrics reports two numbers produced by different parts of the engine. width is the sum of the glyph advances the shaper accumulated… - main-thread metrics === Worker metrics
worker-vs-mainThe same five strings are measured at 12px Arial twice: once on a main-thread 2D canvas, and once inside a dedicated Worker on an… - clientWidth and offsetWidth equal the box the element itself reports
layout-box-arithmeticclientWidth and offsetWidth are not opinions the browser offers — CSSOM defines them as arithmetic over values the same element hands you… - a box placed at the viewport origin measures its origin as zero
client-rect-origin-vs-positionZero is scale-invariant, and that single property is the whole check. - SVG's screen matrix agrees with the element's client rect
svg-ctm-vs-client-rectTwo independent routes to a single fact. getScreenCTM maps an SVG element's user space into viewport coordinates, and getBoundingClientRect… - IntersectionObserver's rect agrees with getBoundingClientRect
client-rect-vs-observerA third account of where one element sits, from the most ordinary API that has one.
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 Render & GPU 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 Render & GPU — the family bcr-vs-range belongs to.