Quick answer
What this guide helps you determine
Understand why some multi-key combinations disappear and how a keyboard matrix differs from browser event handling.
Begin with the observable browser result, repeat it under the same conditions, and change one connection, setting or application at a time. A browser result narrows likely causes but does not certify hardware or decide a repair.
Scope of this check
Keyboard ghosting describes an unintended key report, while blocking describes a real key that is not reported in a combination. People often use “ghosting” for both. A browser test can show the events it receives, but it cannot see the keyboard matrix scan before those events reach the operating system.
Step-by-step method
- Begin with two-key pairs that register reliably, then add one key at a time. Use combinations that matter for your work or games instead of pressing an arbitrary handful, because matrix limits are usually combination-specific.
- Watch the live pressed-key list and maximum simultaneous count. If a key disappears only when a particular third key is added, release everything and repeat the exact order several times to distinguish a stable matrix limitation from a missed press.
- Compare the same combination in a second browser and, if the keyboard supports multiple connection modes, compare those modes. Reserved system shortcuts and accessibility input can intercept combinations before the page receives them.
What to check first
Use these checkpoints to keep the comparison focused. Record the visible behavior rather than assigning a fault label too early.
- Compare problem combinations with simple pairs
- Distinguish blocking from phantom input
- Treat browser results as observations, not certification
How to read what you see
| Observation | What it can suggest | Useful next check |
|---|---|---|
| A real key disappears only in one repeatable combination | The keyboard matrix or firmware may block that combination. | Test an alternative binding and consult the model rollover documentation. |
| An extra key appears that was not pressed | This matches the strict meaning of ghosting, though modern firmware often suppresses it. | Repeat carefully and compare outside the browser before reporting it. |
| The combination fails only in one browser or application | Software handling or a reserved shortcut is more likely than the matrix. | Change the shortcut or compare a neutral text/input tool. |
Common mistakes to avoid
- Do not use a random maximum key count as the only result.
- Do not confuse a sticky pressed indicator caused by lost focus with a physical key held down.
- Do not claim NKRO certification from a browser observation.
Build evidence another person can use
Write down the exact action, visible result and whether it repeats. Include the browser family, operating-system family, connection type and the single comparison that changed the result. Quote the observation directly—for example, “A real key disappears only in one repeatable combination”—then add where it occurred and which comparison changed it.
Change one condition per comparison and return settings that have no effect. Follow model-specific manufacturer instructions before firmware changes, cleaning, disassembly or warranty action.
When to seek qualified support
If the same problem remains in multiple applications and on another compatible connection or computer, collect the repeatable observations and contact the manufacturer or a qualified technician. Stop using equipment that is physically damaged, unusually hot, wet, sparking or unsafe. Device Test Bench cannot inspect electrical condition or make a repair decision.
Privacy during testing
Our public tests process key events, pointer values, media streams and controller input locally. Do not send private recordings, complete typed text or device identifiers when asking for help. A short description of the behavior, browser and page URL is normally enough.
Questions readers ask
Is ghosting the same as low rollover?
No. Rollover is the number or pattern of simultaneous keys reported. Ghosting is an unintended extra report; blocking is a missing intended report.
Why do WASD combinations work while other groups fail?
Keyboard matrices and firmware are often optimized around common gaming groups, so support can vary by key region.
Primary technical references
The following specifications define the browser APIs discussed in this guide. They are primary web-platform references, not product repair manuals.