Keyboard Ghosting Test

Hold several keys together and compare the physical combination with the codes the browser receives; missed keys can reveal a rollover limitation, but the browser cannot inspect the keyboard matrix directly.

Hold several physical keys together

The browser can only show the keys it actually receives.

0Held now

0Max simultaneous

0Unique codes

0Key-up events

Tip: hold a combination on your physical keyboard and confirm every pressed key appears. A missing physical key cannot be inferred by the page—it simply never receives that event.

Test every key Chatter test Repeat rate

What the browser can measure

Start with a functional check, measure only what the browser can actually expose, then retest after one change.

ConnectChoose the actual browser-visible device or grant permission when required.

TestConfirm basic signal, input, output, preview or display behavior.

MeasureUse browser-exposed levels, timing, resolution, FPS, axes or event data.

DiagnoseCompare the symptom with the specific diagnostic instead of relying on one number.

RetestRepeat after changing the device, cable, permission, browser or system setting.

Pre-call Mic Webcam Keyboard Mouse Gamepad Display Permissions

Browser boundary
These tools observe browser APIs and local media/event streams. They cannot certify hardware condition, bypass denied permissions, or expose measurements the browser/OS does not provide.

Keyboard Ghosting Test: Rollover, Combos & Event History

Test simultaneous key rollover, log browser key events, compare common gaming/typing combos and copy an observed ghosting report locally.

Combo profile

History rows

Full keyboard evidence

See held, tested and untested physical key positions

Focus the capture area above, then use this 104-key board to see exactly which KeyboardEvent.code values reached the browser. Session history can be copied or exported as CSV.

0Held now

0Max at once

0/104Positions tested

0Event rows

#	Event	Code	Key	Held

No key events recorded in this v12.77 evidence layer yet. Browser/OS-reserved shortcuts may not reach the page.

Browser-local does not mean laboratory measurement

These pages can report Web API data such as events, stream settings, frame timing and audio samples. They do not certify hardware condition or bypass browser and operating-system limits.

Observed rollover is not mislabeled as certified keyboard rollover

The maximum simultaneous key count means “events received by this browser.” Missing combinations, browser-reserved shortcuts and the physical keyboard matrix cannot be inferred from absent events.

Browser-observed input is not raw hardware telemetry

Keyboard Ghosting Test measures events after they have passed through the device firmware, operating system, browser, event loop, and page. Sampling rate, background load, power-saving behavior, accessibility settings, acceleration, browser coalescing, and display refresh can therefore influence what the page observes.

How to make the test more useful

Repeat the same action several times, close heavy background work, keep the browser focused, and compare patterns rather than treating one sample as a hardware specification. A missing event can indicate rollover or browser behavior without proving an electrical keyboard fault; timing variation can indicate scheduling noise without proving sensor jitter. For warranty, competitive-latency, or hardware diagnostics, confirm findings with the device vendor’s tools or a lower-level measurement method.

Practical guide and verification

Compare the physical keys with the full visual board

The v12.77 board marks every KeyboardEvent.code the browser actually receives, so you can see held keys, previously observed keys and untested positions at a glance. A key you physically hold but never see cannot be reconstructed by software; note that physical discrepancy as the evidence rather than inventing a phantom event.

Separate rollover, blocking and classic ghosting

Limited rollover or matrix blocking commonly causes a physically pressed key to be absent when a combination is held. Classic ghosting is a phantom key that appears even though it was not pressed. A browser can show reported codes, but the person running the test still has to compare them with the physical combination to classify the symptom.

Account for operating-system shortcuts

Some multi-key combinations are reserved by the browser or operating system and may never reach page JavaScript. Repeat a suspicious test with a different combination and, when practical, another browser or computer before concluding that the keyboard matrix itself is responsible.

Use the event history for reproducible comparison

The session history records down/up events, codes, keys and simultaneous count so the same test can be compared after changing a keyboard, connection mode or firmware profile. Exporting the CSV preserves browser-observed evidence; it is not a USB HID trace or certified NKRO measurement.

Test the combinations that matter to the real task

A maximum count alone can hide a bad gaming or productivity chord. Test movement keys plus modifiers, arrow clusters, shortcuts and the exact combinations used in your application. A keyboard that reports many simultaneous letters can still block one important matrix combination.