Keyboard Tester - Rollover vs Anti-Ghosting

Last reviewed 2026-04-27. Open the keyboard test to check your keyboard in the browser - no app install required.

What ghosting actually is

Most low-cost keyboards wire keys into a matrix - rows and columns scanned by the controller. When three keys at the corners of a rectangle in the matrix are held, the controller can read a fourth key at the unused corner that was never pressed. That fourth key is a "ghost". The fix is anti-ghosting circuitry (extra diodes per key) or a different scanning protocol; either way, the keyboard refuses to register the phantom press.

Test for it: hold three keys that share a row and column on the matrix. WASD plus Q is the standard gaming test - on a ghosting-prone keyboard, holding W and A and S while pressing Q makes Q fail or makes a fourth key appear. On a properly anti-ghosted keyboard, every press registers correctly.

What rollover means

N-key rollover is a specification, not an absence of failure. NKRO means every key registers correctly regardless of how many are simultaneously held. 6-key rollover (6KRO) means up to 6 keys plus modifiers register; the 7th press is dropped. 2KRO is the cheapest spec and shows up on bargain keyboards - the moment you hold a third key, things break.

For typing, even 2KRO is fine - most people do not hold three keys at once. For gaming, NKRO is the right pick. For music production with many simultaneous notes, NKRO is required.

How to test in your browser

1. Open the keyboard test. Each physical key shows up on the on-screen keyboard.
2. Hold WASD with one hand and the spacebar with the other. The test should show all five keys highlighted, every one of them.
3. Now hold WASD plus Shift, Ctrl, and a letter key like Q at the same time. Modifier keys often have separate matrix wiring; this checks that gaming-style chord inputs work.
4. Release; the highlights should clear. A key that stays "down" after you release indicates a stuck switch or a debounce problem in the controller.

What the browser test cannot check

The OS sits between the keyboard and the browser. A few things the browser cannot see directly:

• USB report rate. Keyboards report at 125 Hz, 500 Hz, or 1000 Hz. The browser sees press events as they arrive but cannot meaningfully measure intervals at that resolution.
• Hardware key remapping. Some keyboards (Apple's, gaming keyboards with onboard memory) remap keys at the firmware layer. The browser sees the remapped key, not the physical one.
• Wireless dropout. Bluetooth and 2.4 GHz wireless can drop or repeat keys under interference. The test will surface obvious failures but cannot diagnose the radio.

For other device tests see device test checklist for remote work, or run them individually at the device test tools hub.