Every worker realm reports the same GPU as the window
Check id worker-gpu-agrees
What an ordinary browser yields
An ordinary browser: the worker's UNMASKED_RENDERER_WEBGL string matches the window's exactly — pass, severity warn.
What a detector infers
Inside each worker the probe creates an OffscreenCanvas(32,32), obtains a webgl (or experimental-webgl) context, and reads UNMASKED_RENDERER_WEBGL via the WEBGL_debug_renderer_info extension — the same parameter the window-side WebGL probe reads from a DOM canvas. The comparison is renderer-string equality between each worker reading and the main-thread renderer; only the renderer is asserted on, not the vendor. The mechanism: the GPU and its driver are process-level facts, so the renderer string a worker sees is produced by the same graphics stack as the window's. When the two disagree, a detector can infer that the WebGL renderer was rewritten in one realm only — typically a getParameter hook injected into the page context, where OffscreenCanvas in a worker never receives it. The unmodified value shows through and names the real hardware. Severity is warn rather than critical because the renderer string is a softer, more environment-dependent signal than the navigator identity — and the case where a worker has no GPU context, or the window reports no renderer, is not a fail at all: it resolves to pass:null, not applicable.
How to resolve it
If the renderer strings are being overridden, apply the same override in the worker realm as well, or leave them native. If no worker reports a GPU (OffscreenCanvas/WebGL unavailable there) or the window has no renderer, the check renders pass:null — not applicable.
Read in the wild by
CreepJS
CreepJS, an open-source research demo rather than a production detector, builds an OffscreenCanvas WebGL context inside the worker scope and reads UNMASKED_RENDERER_WEBGL there via the WEBGL_debug_renderer_info extension, returning it as `webglRenderer` in the worker payload; its headless module compares that string against the window's renderer — renderer only, not the vendor it also collects — as the `stealth.hasBadWebGL` signal.
src/worker/index.ts (getWebglData, ~lines 95-104): `const canvasOffscreenWebgl = new OffscreenCanvas(256, 256)`; `const contextWebgl = canvasOffscreenWebgl.getContext('webgl')`; `const rendererInfo = contextWebgl.getExtension('WEBGL_debug_renderer_info')`; returns `webglRenderer: contextWebgl.getParameter(rendererInfo.UNMASKED_RENDERER_WEBGL)`, surfaced as `webglRenderer` in the worker payload (line 233). src/headless/index.ts (`stealth.hasBadWebGL`, ~lines 153-157): `const { UNMASKED_RENDERER_WEBGL: gpu } = webgl?.parameters || {}` / `const { webglRenderer: workerGPU } = workerScope || {}` / `return (gpu && workerGPU && (gpu !== workerGPU))`. Source: https://github.com/abrahamjuliot/creepjs
Every attribution traces to a published artifact. See the sources and their limits.
Other checks in Worker realms
- Every worker realm reports the same identity as the window
worker-realms-agreeA page is not one JavaScript realm — it is several. The audit loads one probe script into all three worker kinds the platform offers: a… - Worker scopes available to compare against the window
worker-scopes-reachedThis row asserts nothing — pass is hardcoded null and severity is info.
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 Worker realms 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 Worker realms — the family worker-gpu-agrees belongs to.