Environment & locale

navigator.pdfViewerEnabled is true

Pim· Clearcote Research 1 min readCheck id pdf-viewer

true on a desktop Chrome profile with the built-in viewer; false or absent is legitimate on mobile, WebKit, or policy-restricted builds.

What a detector infers

A direct read of `navigator.pdfViewerEnabled`. It is N/A when the property is not exposed at all, passes when true, and is marked false otherwise — at 'info' severity, so it is contextual and not scored. On its own the flag proves little: false is entirely normal on mobile Chrome, on WebKit, and wherever enterprise policy disables the built-in viewer.

Its real job in this audit is to supply the premise for the plugins check above, which only demands a populated plugin array when this flag claims a viewer exists. Read the two lines together, not separately.

How to resolve it

No fix required in isolation — this is a reading, not a verdict. Only act on it if it contradicts the plugin list (see has-plugins) or the platform you are presenting.

What is a headless browser?

Read in the wild by

PerimeterX / HUMAN

Collects navigator.pdfViewerEnabled as its own boolean field, in the same payload that separately carries the navigator.plugins name list and plugin count.

CreepJS

CreepJS, a research demo rather than a production detector, reads navigator.pdfViewerEnabled and counts a false reading toward its "like headless" rating.

src/headless/index.ts — inside the `likeHeadless` object: `pdfIsDisabled: ('pdfViewerEnabled' in navigator && navigator.pdfViewerEnabled === false)`, scored via `likeHeadlessRating = +((likeHeadlessKeys.filter((key) => likeHeadless[key]).length / likeHeadlessKeys.length) * 100).toFixed(0)`

Every attribution traces to a published artifact. See the sources and their limits.

Nearby checks in Environment & locale

See all 28 checks in Environment & locale

Run this check on your browser All 272 checks How the test works

Who builds this test

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 pdf-viewer belongs to.